diff --git a/lib/Controller/EndpointController.php b/lib/Controller/EndpointController.php
index d931b178e..acbe1a795 100644
--- a/lib/Controller/EndpointController.php
+++ b/lib/Controller/EndpointController.php
@@ -191,6 +191,11 @@ public function confirmIdsForUser(string $apiVersion, array $ids): DataResponse
 			return new DataResponse([], Http::STATUS_BAD_REQUEST);
 		}
 
+		$ids = array_unique(array_filter(array_map(
+			static fn ($id) => is_numeric($id) ? (int) $id : 0,
+			$ids
+		)));
+
 		$existingIds = $this->handler->confirmIdsForUser($this->getCurrentUser(), $ids);
 		return new DataResponse($existingIds, Http::STATUS_OK);
 	}