diff --git a/apps/files_sharing/api/sharees.php b/apps/files_sharing/api/sharees.php
index 9e324078da..734c267020 100644
--- a/apps/files_sharing/api/sharees.php
+++ b/apps/files_sharing/api/sharees.php
@@ -62,6 +62,9 @@ class Sharees {
 	/** @var bool */
 	protected $shareWithGroupOnly = false;
 
+	/** @var bool */
+	protected $shareeEnumeration = true;
+
 	/** @var int */
 	protected $offset = 0;
 
@@ -134,7 +137,7 @@ class Sharees {
 			}
 		}
 
-		if (sizeof($users) < $this->limit) {
+		if (!$this->shareeEnumeration || sizeof($users) < $this->limit) {
 			$this->reachedEndFor[] = 'users';
 		}
 
@@ -176,6 +179,10 @@ class Sharees {
 				]);
 			}
 		}
+
+		if (!$this->shareeEnumeration) {
+			$this->result['users'] = [];
+		}
 	}
 
 	/**
@@ -187,7 +194,7 @@ class Sharees {
 		$groups = $this->groupManager->search($search, $this->limit, $this->offset);
 		$groups = array_map(function (IGroup $group) { return $group->getGID(); }, $groups);
 
-		if (sizeof($groups) < $this->limit) {
+		if (!$this->shareeEnumeration || sizeof($groups) < $this->limit) {
 			$this->reachedEndFor[] = 'groups';
 		}
 
@@ -233,6 +240,10 @@ class Sharees {
 				]);
 			}
 		}
+
+		if (!$this->shareeEnumeration) {
+			$this->result['groups'] = [];
+		}
 	}
 
 	/**
@@ -273,6 +284,10 @@ class Sharees {
 			}
 		}
 
+		if (!$this->shareeEnumeration) {
+			$this->result['remotes'] = [];
+		}
+
 		if (!$foundRemoteById && substr_count($search, '@') >= 1 && substr_count($search, ' ') === 0 && $this->offset === 0) {
 			$this->result['exact']['remotes'][] = [
 				'label' => $search,
@@ -322,6 +337,7 @@ class Sharees {
 		}
 
 		$this->shareWithGroupOnly = $this->config->getAppValue('core', 'shareapi_only_share_with_group_members', 'no') === 'yes';
+		$this->shareeEnumeration = $this->config->getAppValue('core', 'shareapi_allow_share_dialog_user_enumeration', 'yes') === 'yes';
 		$this->limit = (int) $perPage;
 		$this->offset = $perPage * ($page - 1);
 
diff --git a/apps/files_sharing/tests/api/shareestest.php b/apps/files_sharing/tests/api/shareestest.php
index 5c5d5b0d30..91b8b1c7e6 100644
--- a/apps/files_sharing/tests/api/shareestest.php
+++ b/apps/files_sharing/tests/api/shareestest.php
@@ -110,16 +110,30 @@ class ShareesTest extends TestCase {
 
 	public function dataGetUsers() {
 		return [
-			['test', false, [], [], [], [], true, false],
-			['test', true, [], [], [], [], true, false],
+			['test', false, true, [], [], [], [], true, false],
+			['test', false, false, [], [], [], [], true, false],
+			['test', true, true, [], [], [], [], true, false],
+			['test', true, false, [], [], [], [], true, false],
 			[
-				'test', false, [], [],
+				'test', false, true, [], [],
 				[
 					['label' => 'Test', 'value' => ['shareType' => Share::SHARE_TYPE_USER, 'shareWith' => 'test']],
 				], [], true, $this->getUserMock('test', 'Test')
 			],
 			[
-				'test', true, [], [],
+				'test', false, false, [], [],
+				[
+					['label' => 'Test', 'value' => ['shareType' => Share::SHARE_TYPE_USER, 'shareWith' => 'test']],
+				], [], true, $this->getUserMock('test', 'Test')
+			],
+			[
+				'test', true, true, [], [],
+				[
+					['label' => 'Test', 'value' => ['shareType' => Share::SHARE_TYPE_USER, 'shareWith' => 'test']],
+				], [], true, $this->getUserMock('test', 'Test')
+			],
+			[
+				'test', true, false, [], [],
 				[
 					['label' => 'Test', 'value' => ['shareType' => Share::SHARE_TYPE_USER, 'shareWith' => 'test']],
 				], [], true, $this->getUserMock('test', 'Test')
@@ -127,6 +141,7 @@ class ShareesTest extends TestCase {
 			[
 				'test',
 				false,
+				true,
 				[],
 				[
 					$this->getUserMock('test1', 'Test One'),
@@ -141,6 +156,20 @@ class ShareesTest extends TestCase {
 			[
 				'test',
 				false,
+				false,
+				[],
+				[
+					$this->getUserMock('test1', 'Test One'),
+				],
+				[],
+				[],
+				true,
+				false,
+			],
+			[
+				'test',
+				false,
+				true,
 				[],
 				[
 					$this->getUserMock('test1', 'Test One'),
@@ -157,6 +186,21 @@ class ShareesTest extends TestCase {
 			[
 				'test',
 				false,
+				false,
+				[],
+				[
+					$this->getUserMock('test1', 'Test One'),
+					$this->getUserMock('test2', 'Test Two'),
+				],
+				[],
+				[],
+				true,
+				false,
+			],
+			[
+				'test',
+				false,
+				true,
 				[],
 				[
 					$this->getUserMock('test0', 'Test'),
@@ -175,6 +219,24 @@ class ShareesTest extends TestCase {
 			],
 			[
 				'test',
+				false,
+				false,
+				[],
+				[
+					$this->getUserMock('test0', 'Test'),
+					$this->getUserMock('test1', 'Test One'),
+					$this->getUserMock('test2', 'Test Two'),
+				],
+				[
+					['label' => 'Test', 'value' => ['shareType' => Share::SHARE_TYPE_USER, 'shareWith' => 'test0']],
+				],
+				[],
+				true,
+				false,
+			],
+			[
+				'test',
+				true,
 				true,
 				['abc', 'xyz'],
 				[
@@ -191,6 +253,21 @@ class ShareesTest extends TestCase {
 			[
 				'test',
 				true,
+				false,
+				['abc', 'xyz'],
+				[
+					['abc', 'test', 2, 0, ['test1' => 'Test One']],
+					['xyz', 'test', 2, 0, []],
+				],
+				[],
+				[],
+				true,
+				false,
+			],
+			[
+				'test',
+				true,
+				true,
 				['abc', 'xyz'],
 				[
 					['abc', 'test', 2, 0, [
@@ -213,6 +290,27 @@ class ShareesTest extends TestCase {
 			[
 				'test',
 				true,
+				false,
+				['abc', 'xyz'],
+				[
+					['abc', 'test', 2, 0, [
+						'test1' => 'Test One',
+						'test2' => 'Test Two',
+					]],
+					['xyz', 'test', 2, 0, [
+						'test1' => 'Test One',
+						'test2' => 'Test Two',
+					]],
+				],
+				[],
+				[],
+				true,
+				false,
+			],
+			[
+				'test',
+				true,
+				true,
 				['abc', 'xyz'],
 				[
 					['abc', 'test', 2, 0, [
@@ -231,6 +329,26 @@ class ShareesTest extends TestCase {
 				false,
 				false,
 			],
+			[
+				'test',
+				true,
+				false,
+				['abc', 'xyz'],
+				[
+					['abc', 'test', 2, 0, [
+						'test' => 'Test One',
+					]],
+					['xyz', 'test', 2, 0, [
+						'test2' => 'Test Two',
+					]],
+				],
+				[
+					['label' => 'Test One', 'value' => ['shareType' => Share::SHARE_TYPE_USER, 'shareWith' => 'test']],
+				],
+				[],
+				true,
+				false,
+			],
 		];
 	}
 
@@ -239,6 +357,7 @@ class ShareesTest extends TestCase {
 	 *
 	 * @param string $searchTerm
 	 * @param bool $shareWithGroupOnly
+	 * @param bool $shareeEnumeration
 	 * @param array $groupResponse
 	 * @param array $userResponse
 	 * @param array $exactExpected
@@ -246,10 +365,11 @@ class ShareesTest extends TestCase {
 	 * @param bool $reachedEnd
 	 * @param mixed $singleUser
 	 */
-	public function testGetUsers($searchTerm, $shareWithGroupOnly, $groupResponse, $userResponse, $exactExpected, $expected, $reachedEnd, $singleUser) {
+	public function testGetUsers($searchTerm, $shareWithGroupOnly, $shareeEnumeration, $groupResponse, $userResponse, $exactExpected, $expected, $reachedEnd, $singleUser) {
 		$this->invokePrivate($this->sharees, 'limit', [2]);
 		$this->invokePrivate($this->sharees, 'offset', [0]);
 		$this->invokePrivate($this->sharees, 'shareWithGroupOnly', [$shareWithGroupOnly]);
+		$this->invokePrivate($this->sharees, 'shareeEnumeration', [$shareeEnumeration]);
 
 		$user = $this->getUserMock('admin', 'Administrator');
 		$this->session->expects($this->any())
@@ -290,9 +410,10 @@ class ShareesTest extends TestCase {
 
 	public function dataGetGroups() {
 		return [
-			['test', false, [], [], [], [], true, false],
+			['test', false, true, [], [], [], [], true, false],
+			['test', false, false, [], [], [], [], true, false],
 			[
-				'test', false,
+				'test', false, true,
 				[$this->getGroupMock('test1')],
 				[],
 				[],
@@ -301,7 +422,16 @@ class ShareesTest extends TestCase {
 				false,
 			],
 			[
-				'test', false,
+				'test', false, false,
+				[$this->getGroupMock('test1')],
+				[],
+				[],
+				[],
+				true,
+				false,
+			],
+			[
+				'test', false, true,
 				[
 					$this->getGroupMock('test'),
 					$this->getGroupMock('test1'),
@@ -313,7 +443,19 @@ class ShareesTest extends TestCase {
 				false,
 			],
 			[
-				'test', false,
+				'test', false, false,
+				[
+					$this->getGroupMock('test'),
+					$this->getGroupMock('test1'),
+				],
+				[],
+				[['label' => 'test', 'value' => ['shareType' => Share::SHARE_TYPE_GROUP, 'shareWith' => 'test']]],
+				[],
+				true,
+				false,
+			],
+			[
+				'test', false, true,
 				[
 					$this->getGroupMock('test0'),
 					$this->getGroupMock('test1'),
@@ -328,7 +470,19 @@ class ShareesTest extends TestCase {
 				null,
 			],
 			[
-				'test', false,
+				'test', false, false,
+				[
+					$this->getGroupMock('test0'),
+					$this->getGroupMock('test1'),
+				],
+				[],
+				[],
+				[],
+				true,
+				null,
+			],
+			[
+				'test', false, true,
 				[
 					$this->getGroupMock('test0'),
 					$this->getGroupMock('test1'),
@@ -344,9 +498,24 @@ class ShareesTest extends TestCase {
 				false,
 				$this->getGroupMock('test'),
 			],
-			['test', true, [], [], [], [], true, false],
 			[
-				'test', true,
+				'test', false, false,
+				[
+					$this->getGroupMock('test0'),
+					$this->getGroupMock('test1'),
+				],
+				[],
+				[
+					['label' => 'test', 'value' => ['shareType' => Share::SHARE_TYPE_GROUP, 'shareWith' => 'test']],
+				],
+				[],
+				true,
+				$this->getGroupMock('test'),
+			],
+			['test', true, true, [], [], [], [], true, false],
+			['test', true, false, [], [], [], [], true, false],
+			[
+				'test', true, true,
 				[
 					$this->getGroupMock('test1'),
 					$this->getGroupMock('test2'),
@@ -358,7 +527,19 @@ class ShareesTest extends TestCase {
 				false,
 			],
 			[
-				'test', true,
+				'test', true, false,
+				[
+					$this->getGroupMock('test1'),
+					$this->getGroupMock('test2'),
+				],
+				[$this->getGroupMock('test1')],
+				[],
+				[],
+				true,
+				false,
+			],
+			[
+				'test', true, true,
 				[
 					$this->getGroupMock('test'),
 					$this->getGroupMock('test1'),
@@ -370,7 +551,19 @@ class ShareesTest extends TestCase {
 				false,
 			],
 			[
-				'test', true,
+				'test', true, false,
+				[
+					$this->getGroupMock('test'),
+					$this->getGroupMock('test1'),
+				],
+				[$this->getGroupMock('test')],
+				[['label' => 'test', 'value' => ['shareType' => Share::SHARE_TYPE_GROUP, 'shareWith' => 'test']]],
+				[],
+				true,
+				false,
+			],
+			[
+				'test', true, true,
 				[
 					$this->getGroupMock('test'),
 					$this->getGroupMock('test1'),
@@ -382,7 +575,19 @@ class ShareesTest extends TestCase {
 				false,
 			],
 			[
-				'test', true,
+				'test', true, false,
+				[
+					$this->getGroupMock('test'),
+					$this->getGroupMock('test1'),
+				],
+				[$this->getGroupMock('test1')],
+				[],
+				[],
+				true,
+				false,
+			],
+			[
+				'test', true, true,
 				[
 					$this->getGroupMock('test'),
 					$this->getGroupMock('test1'),
@@ -394,7 +599,19 @@ class ShareesTest extends TestCase {
 				false,
 			],
 			[
-				'test', true,
+				'test', true, false,
+				[
+					$this->getGroupMock('test'),
+					$this->getGroupMock('test1'),
+				],
+				[$this->getGroupMock('test'), $this->getGroupMock('test0'), $this->getGroupMock('test1')],
+				[['label' => 'test', 'value' => ['shareType' => Share::SHARE_TYPE_GROUP, 'shareWith' => 'test']]],
+				[],
+				true,
+				false,
+			],
+			[
+				'test', true, true,
 				[
 					$this->getGroupMock('test0'),
 					$this->getGroupMock('test1'),
@@ -409,7 +626,19 @@ class ShareesTest extends TestCase {
 				null,
 			],
 			[
-				'test', true,
+				'test', true, false,
+				[
+					$this->getGroupMock('test0'),
+					$this->getGroupMock('test1'),
+				],
+				[$this->getGroupMock('test'), $this->getGroupMock('test0'), $this->getGroupMock('test1')],
+				[],
+				[],
+				true,
+				null,
+			],
+			[
+				'test', true, true,
 				[
 					$this->getGroupMock('test0'),
 					$this->getGroupMock('test1'),
@@ -425,6 +654,20 @@ class ShareesTest extends TestCase {
 				false,
 				$this->getGroupMock('test'),
 			],
+			[
+				'test', true, false,
+				[
+					$this->getGroupMock('test0'),
+					$this->getGroupMock('test1'),
+				],
+				[$this->getGroupMock('test'), $this->getGroupMock('test0'), $this->getGroupMock('test1')],
+				[
+					['label' => 'test', 'value' => ['shareType' => Share::SHARE_TYPE_GROUP, 'shareWith' => 'test']],
+				],
+				[],
+				true,
+				$this->getGroupMock('test'),
+			],
 		];
 	}
 
@@ -433,6 +676,7 @@ class ShareesTest extends TestCase {
 	 *
 	 * @param string $searchTerm
 	 * @param bool $shareWithGroupOnly
+	 * @param bool $shareeEnumeration
 	 * @param array $groupResponse
 	 * @param array $userGroupsResponse
 	 * @param array $exactExpected
@@ -440,10 +684,11 @@ class ShareesTest extends TestCase {
 	 * @param bool $reachedEnd
 	 * @param mixed $singleGroup
 	 */
-	public function testGetGroups($searchTerm, $shareWithGroupOnly, $groupResponse, $userGroupsResponse, $exactExpected, $expected, $reachedEnd, $singleGroup) {
+	public function testGetGroups($searchTerm, $shareWithGroupOnly, $shareeEnumeration, $groupResponse, $userGroupsResponse, $exactExpected, $expected, $reachedEnd, $singleGroup) {
 		$this->invokePrivate($this->sharees, 'limit', [2]);
 		$this->invokePrivate($this->sharees, 'offset', [0]);
 		$this->invokePrivate($this->sharees, 'shareWithGroupOnly', [$shareWithGroupOnly]);
+		$this->invokePrivate($this->sharees, 'shareeEnumeration', [$shareeEnumeration]);
 
 		$this->groupManager->expects($this->once())
 			->method('search')
@@ -480,10 +725,22 @@ class ShareesTest extends TestCase {
 
 	public function dataGetRemote() {
 		return [
-			['test', [], [], [], true],
+			['test', [], true, [], [], true],
+			['test', [], false, [], [], true],
 			[
 				'test@remote',
 				[],
+				true,
+				[
+					['label' => 'test@remote', 'value' => ['shareType' => Share::SHARE_TYPE_REMOTE, 'shareWith' => 'test@remote']],
+				],
+				[],
+				true,
+			],
+			[
+				'test@remote',
+				[],
+				false,
 				[
 					['label' => 'test@remote', 'value' => ['shareType' => Share::SHARE_TYPE_REMOTE, 'shareWith' => 'test@remote']],
 				],
@@ -508,12 +765,63 @@ class ShareesTest extends TestCase {
 						],
 					],
 				],
+				true,
 				[],
 				[
 					['label' => 'User @ Localhost', 'value' => ['shareType' => Share::SHARE_TYPE_REMOTE, 'shareWith' => 'username@localhost']],
 				],
 				true,
 			],
+			[
+				'test',
+				[
+					[
+						'FN' => 'User3 @ Localhost',
+					],
+					[
+						'FN' => 'User2 @ Localhost',
+						'CLOUD' => [
+						],
+					],
+					[
+						'FN' => 'User @ Localhost',
+						'CLOUD' => [
+							'username@localhost',
+						],
+					],
+				],
+				false,
+				[],
+				[],
+				true,
+			],
+			[
+				'test@remote',
+				[
+					[
+						'FN' => 'User3 @ Localhost',
+					],
+					[
+						'FN' => 'User2 @ Localhost',
+						'CLOUD' => [
+						],
+					],
+					[
+						'FN' => 'User @ Localhost',
+						'CLOUD' => [
+							'username@localhost',
+						],
+					],
+				],
+				true,
+				[
+					['label' => 'test@remote', 'value' => ['shareType' => Share::SHARE_TYPE_REMOTE, 'shareWith' => 'test@remote']],
+				],
+				[
+					['label' => 'User @ Localhost', 'value' => ['shareType' => Share::SHARE_TYPE_REMOTE, 'shareWith' => 'username@localhost']],
+				],
+				true,
+			],
 			[
 				'test@remote',
 				[
@@ -532,12 +840,11 @@ class ShareesTest extends TestCase {
 						],
 					],
 				],
+				false,
 				[
 					['label' => 'test@remote', 'value' => ['shareType' => Share::SHARE_TYPE_REMOTE, 'shareWith' => 'test@remote']],
 				],
-				[
-					['label' => 'User @ Localhost', 'value' => ['shareType' => Share::SHARE_TYPE_REMOTE, 'shareWith' => 'username@localhost']],
-				],
+				[],
 				true,
 			],
 			[
@@ -558,11 +865,36 @@ class ShareesTest extends TestCase {
 						],
 					],
 				],
+				true,
 				[
 					['label' => 'User @ Localhost', 'value' => ['shareType' => Share::SHARE_TYPE_REMOTE, 'shareWith' => 'username@localhost']],
 				],
+				[],
+				true,
+			],
+			[
+				'username@localhost',
 				[
+					[
+						'FN' => 'User3 @ Localhost',
+					],
+					[
+						'FN' => 'User2 @ Localhost',
+						'CLOUD' => [
+						],
+					],
+					[
+						'FN' => 'User @ Localhost',
+						'CLOUD' => [
+							'username@localhost',
+						],
+					],
 				],
+				false,
+				[
+					['label' => 'User @ Localhost', 'value' => ['shareType' => Share::SHARE_TYPE_REMOTE, 'shareWith' => 'username@localhost']],
+				],
+				[],
 				true,
 			],
 		];
@@ -573,11 +905,13 @@ class ShareesTest extends TestCase {
 	 *
 	 * @param string $searchTerm
 	 * @param array $contacts
+	 * @param bool $shareeEnumeration
 	 * @param array $exactExpected
 	 * @param array $expected
 	 * @param bool $reachedEnd
 	 */
-	public function testGetRemote($searchTerm, $contacts, $exactExpected, $expected, $reachedEnd) {
+	public function testGetRemote($searchTerm, $contacts, $shareeEnumeration, $exactExpected, $expected, $reachedEnd) {
+		$this->invokePrivate($this->sharees, 'shareeEnumeration', [$shareeEnumeration]);
 		$this->contactsManager->expects($this->any())
 			->method('search')
 			->with($searchTerm, ['CLOUD', 'FN'])
@@ -595,80 +929,84 @@ class ShareesTest extends TestCase {
 		$allTypes = [Share::SHARE_TYPE_USER, Share::SHARE_TYPE_GROUP, Share::SHARE_TYPE_REMOTE];
 
 		return [
-			[[], '', true, '', null, $allTypes, 1, 200, false],
+			[[], '', 'yes', true, '', null, $allTypes, 1, 200, false, true],
 
 			// Test itemType
 			[[
 				'search' => '',
-			], '', true, '', null, $allTypes, 1, 200, false],
+			], '', 'yes', true, '', null, $allTypes, 1, 200, false, true],
 			[[
 				'search' => 'foobar',
-			], '', true, 'foobar', null, $allTypes, 1, 200, false],
+			], '', 'yes', true, 'foobar', null, $allTypes, 1, 200, false, true],
 			[[
 				'search' => 0,
-			], '', true, '0', null, $allTypes, 1, 200, false],
+			], '', 'yes', true, '0', null, $allTypes, 1, 200, false, true],
 
 			// Test itemType
 			[[
 				'itemType' => '',
-			], '', true, '', '', $allTypes, 1, 200, false],
+			], '', 'yes', true, '', '', $allTypes, 1, 200, false, true],
 			[[
 				'itemType' => 'folder',
-			], '', true, '', 'folder', $allTypes, 1, 200, false],
+			], '', 'yes', true, '', 'folder', $allTypes, 1, 200, false, true],
 			[[
 				'itemType' => 0,
-			], '', true, '', '0', $allTypes, 1, 200, false],
+			], '', 'yes', true, '', '0', $allTypes, 1, 200, false, true],
 
 			// Test shareType
 			[[
-			], '', true, '', null, $allTypes, 1, 200, false],
+			], '', 'yes', true, '', null, $allTypes, 1, 200, false, true],
 			[[
 				'shareType' => 0,
-			], '', true, '', null, [0], 1, 200, false],
+			], '', 'yes', true, '', null, [0], 1, 200, false, true],
 			[[
 				'shareType' => '0',
-			], '', true, '', null, [0], 1, 200, false],
+			], '', 'yes', true, '', null, [0], 1, 200, false, true],
 			[[
 				'shareType' => 1,
-			], '', true, '', null, [1], 1, 200, false],
+			], '', 'yes', true, '', null, [1], 1, 200, false, true],
 			[[
 				'shareType' => 12,
-			], '', true, '', null, [], 1, 200, false],
+			], '', 'yes', true, '', null, [], 1, 200, false, true],
 			[[
 				'shareType' => 'foobar',
-			], '', true, '', null, $allTypes, 1, 200, false],
+			], '', 'yes', true, '', null, $allTypes, 1, 200, false, true],
 			[[
 				'shareType' => [0, 1, 2],
-			], '', true, '', null, [0, 1], 1, 200, false],
+			], '', 'yes', true, '', null, [0, 1], 1, 200, false, true],
 			[[
 				'shareType' => [0, 1],
-			], '', true, '', null, [0, 1], 1, 200, false],
+			], '', 'yes', true, '', null, [0, 1], 1, 200, false, true],
 			[[
 				'shareType' => $allTypes,
-			], '', true, '', null, $allTypes, 1, 200, false],
+			], '', 'yes', true, '', null, $allTypes, 1, 200, false, true],
 			[[
 				'shareType' => $allTypes,
-			], '', false, '', null, [0, 1], 1, 200, false],
+			], '', 'yes', false, '', null, [0, 1], 1, 200, false, true],
 
 			// Test pagination
 			[[
 				'page' => 1,
-			], '', true, '', null, $allTypes, 1, 200, false],
+			], '', 'yes', true, '', null, $allTypes, 1, 200, false, true],
 			[[
 				'page' => 10,
-			], '', true, '', null, $allTypes, 10, 200, false],
+			], '', 'yes', true, '', null, $allTypes, 10, 200, false, true],
 
 			// Test perPage
 			[[
 				'perPage' => 1,
-			], '', true, '', null, $allTypes, 1, 1, false],
+			], '', 'yes', true, '', null, $allTypes, 1, 1, false, true],
 			[[
 				'perPage' => 10,
-			], '', true, '', null, $allTypes, 1, 10, false],
+			], '', 'yes', true, '', null, $allTypes, 1, 10, false, true],
 
 			// Test $shareWithGroupOnly setting
-			[[], 'no', true, '', null, $allTypes, 1, 200, false],
-			[[], 'yes', true, '', null, $allTypes, 1, 200, true],
+			[[], 'no', 'yes',  true, '', null, $allTypes, 1, 200, false, true],
+			[[], 'yes', 'yes', true, '', null, $allTypes, 1, 200, true, true],
+
+			// Test $shareeEnumeration setting
+			[[], 'no', 'yes',  true, '', null, $allTypes, 1, 200, false, true],
+			[[], 'no', 'no', true, '', null, $allTypes, 1, 200, false, false],
 
 		];
 	}
@@ -678,6 +1016,7 @@ class ShareesTest extends TestCase {
 	 *
 	 * @param array $getData
 	 * @param string $apiSetting
+	 * @param string $enumSetting
 	 * @param bool $remoteSharingEnabled
 	 * @param string $search
 	 * @param string $itemType
@@ -685,18 +1024,22 @@ class ShareesTest extends TestCase {
 	 * @param int $page
 	 * @param int $perPage
 	 * @param bool $shareWithGroupOnly
+	 * @param bool $shareeEnumeration
 	 */
-	public function testSearch($getData, $apiSetting, $remoteSharingEnabled, $search, $itemType, $shareTypes, $page, $perPage, $shareWithGroupOnly) {
+	public function testSearch($getData, $apiSetting, $enumSetting, $remoteSharingEnabled, $search, $itemType, $shareTypes, $page, $perPage, $shareWithGroupOnly, $shareeEnumeration) {
 		$oldGet = $_GET;
 		$_GET = $getData;
 
 		$config = $this->getMockBuilder('OCP\IConfig')
 			->disableOriginalConstructor()
 			->getMock();
-		$config->expects($this->once())
+		$config->expects($this->exactly(2))
 			->method('getAppValue')
-			->with('core', 'shareapi_only_share_with_group_members', 'no')
-			->willReturn($apiSetting);
+			->with('core', $this->anything(), $this->anything())
+			->willReturnMap([
+				['core', 'shareapi_only_share_with_group_members', 'no', $apiSetting],
+				['core', 'shareapi_allow_share_dialog_user_enumeration', 'yes', $enumSetting],
+			]);
 
 		$sharees = $this->getMockBuilder('\OCA\Files_Sharing\API\Sharees')
 			->setConstructorArgs([
@@ -735,6 +1078,7 @@ class ShareesTest extends TestCase {
 		$this->assertInstanceOf('\OC_OCS_Result', $sharees->search());
 
 		$this->assertSame($shareWithGroupOnly, $this->invokePrivate($sharees, 'shareWithGroupOnly'));
+		$this->assertSame($shareeEnumeration, $this->invokePrivate($sharees, 'shareeEnumeration'));
 
 		$_GET = $oldGet;
 	}
diff --git a/core/ajax/share.php b/core/ajax/share.php
index 69b84564ab..4546217def 100644
--- a/core/ajax/share.php
+++ b/core/ajax/share.php
@@ -379,6 +379,16 @@ if (isset($_POST['action']) && isset($_POST['itemType']) && isset($_POST['itemSo
 					}
 				}
 
+				$sharingAutocompletion = \OC::$server->getConfig()
+					->getAppValue('core', 'shareapi_allow_share_dialog_user_enumeration', 'yes');
+
+				if ($sharingAutocompletion !== 'yes') {
+					$searchTerm = strtolower($_GET['search']);
+					$shareWith = array_filter($shareWith, function($user) use ($searchTerm) {
+						return strtolower($user['label']) === $searchTerm
+							|| strtolower($user['value']['shareWith']) === $searchTerm;
+					});
+				}
 
 				$sorter = new \OC\Share\SearchResultSorter((string)$_GET['search'],
 														   'label',
diff --git a/settings/admin.php b/settings/admin.php
index 38683438f3..c8bf1d3274 100644
--- a/settings/admin.php
+++ b/settings/admin.php
@@ -122,6 +122,7 @@ $template->assign('allowPublicUpload', $appConfig->getValue('core', 'shareapi_al
 $template->assign('allowResharing', $appConfig->getValue('core', 'shareapi_allow_resharing', 'yes'));
 $template->assign('allowPublicMailNotification', $appConfig->getValue('core', 'shareapi_allow_public_notification', 'no'));
 $template->assign('allowMailNotification', $appConfig->getValue('core', 'shareapi_allow_mail_notification', 'no'));
+$template->assign('allowShareDialogUserEnumeration', $appConfig->getValue('core', 'shareapi_allow_share_dialog_user_enumeration', 'yes'));
 $template->assign('onlyShareWithGroupMembers', \OC\Share\Share::shareWithGroupMembersOnly());
 $databaseOverload = (strpos(\OCP\Config::getSystemValue('dbtype'), 'sqlite') !== false);
 $template->assign('databaseOverload', $databaseOverload);
diff --git a/settings/templates/admin.php b/settings/templates/admin.php
index 36088d9f8c..bfb0d5d364 100644
--- a/settings/templates/admin.php
+++ b/settings/templates/admin.php
@@ -265,6 +265,11 @@ if ($_['cronErrors']) {
 			<br />
 			<em><?php p($l->t('These groups will still be able to receive shares, but not to initiate them.')); ?></em>
 		</p>
+		<p class="<?php if ($_['shareAPIEnabled'] === 'no') p('hidden');?>">
+			<input type="checkbox" name="shareapi_allow_share_dialog_user_enumeration" value="1" id="shareapi_allow_share_dialog_user_enumeration"
+				<?php if ($_['allowShareDialogUserEnumeration'] === 'yes') print_unescaped('checked="checked"'); ?> />
+			<label for="shareapi_allow_share_dialog_user_enumeration"><?php p($l->t('Allow username autocompletion in share dialog. If this is disabled the full username needs to be entered.'));?></label><br />
+		</p>
 
 		<?php print_unescaped($_['fileSharingSettings']); ?>
 	</div>