diff --git a/apps/dav/lib/Comments/EntityCollection.php b/apps/dav/lib/Comments/EntityCollection.php
index d9b06e1240c70..cb7556a67ff48 100644
--- a/apps/dav/lib/Comments/EntityCollection.php
+++ b/apps/dav/lib/Comments/EntityCollection.php
@@ -101,6 +101,10 @@ public function getId() {
 	public function getChild($name) {
 		try {
 			$comment = $this->commentsManager->get($name);
+			if ($comment->getObjectType() !== $this->name
+				|| $comment->getObjectId() !== $this->id) {
+				throw new NotFound();
+			}
 			return new CommentNode(
 				$this->commentsManager,
 				$comment,
@@ -154,8 +158,9 @@ public function findChildren($limit = 0, $offset = 0, \DateTime $datetime = null
 	 */
 	public function childExists($name) {
 		try {
-			$this->commentsManager->get($name);
-			return true;
+			$comment = $this->commentsManager->get($name);
+			return $comment->getObjectType() === $this->name
+				&& $comment->getObjectId() === $this->id;
 		} catch (NotFoundException $e) {
 			return false;
 		}
diff --git a/apps/dav/tests/unit/Comments/EntityCollectionTest.php b/apps/dav/tests/unit/Comments/EntityCollectionTest.php
index 4466b0a63074b..9ff75b18fe279 100644
--- a/apps/dav/tests/unit/Comments/EntityCollectionTest.php
+++ b/apps/dav/tests/unit/Comments/EntityCollectionTest.php
@@ -76,14 +76,16 @@ public function testGetId() {
 	}
 
 	public function testGetChild() {
+		$comment = $this->createMock(IComment::class);
+		$comment->method('getObjectType')
+			->willReturn('files');
+		$comment->method('getObjectId')
+			->willReturn('19');
+
 		$this->commentsManager->expects($this->once())
 			->method('get')
 			->with('55')
-			->willReturn(
-				$this->getMockBuilder(IComment::class)
-					->disableOriginalConstructor()
-					->getMock()
-			);
+			->willReturn($comment);
 
 		$node = $this->collection->getChild('55');
 		$this->assertTrue($node instanceof \OCA\DAV\Comments\CommentNode);
@@ -135,6 +137,17 @@ public function testFindChildren() {
 	}
 
 	public function testChildExistsTrue() {
+		$comment = $this->createMock(IComment::class);
+		$comment->method('getObjectType')
+			->willReturn('files');
+		$comment->method('getObjectId')
+			->willReturn('19');
+
+		$this->commentsManager->expects($this->once())
+			->method('get')
+			->with('44')
+			->willReturn($comment);
+
 		$this->assertTrue($this->collection->childExists('44'));
 	}
 
diff --git a/lib/private/DB/QueryBuilder/QueryBuilder.php b/lib/private/DB/QueryBuilder/QueryBuilder.php
index bf5ec2f6bec91..2527b8ddb045c 100644
--- a/lib/private/DB/QueryBuilder/QueryBuilder.php
+++ b/lib/private/DB/QueryBuilder/QueryBuilder.php
@@ -1108,6 +1108,10 @@ public function orHaving(...$having) {
 	 * @return $this This QueryBuilder instance.
 	 */
 	public function orderBy($sort, $order = null) {
+		if ($order !== null && !in_array(strtoupper((string) $order), ['ASC', 'DESC'], true)) {
+			$order = null;
+		}
+
 		$this->queryBuilder->orderBy(
 			$this->helper->quoteColumnName($sort),
 			$order
@@ -1125,6 +1129,10 @@ public function orderBy($sort, $order = null) {
 	 * @return $this This QueryBuilder instance.
 	 */
 	public function addOrderBy($sort, $order = null) {
+		if ($order !== null && !in_array(strtoupper((string) $order), ['ASC', 'DESC'], true)) {
+			$order = null;
+		}
+
 		$this->queryBuilder->addOrderBy(
 			$this->helper->quoteColumnName($sort),
 			$order