diff --git a/lib/Controller/SiteController.php b/lib/Controller/SiteController.php
index c5f3c316..17c90d68 100644
--- a/lib/Controller/SiteController.php
+++ b/lib/Controller/SiteController.php
@@ -100,6 +100,7 @@ protected function createResponse(int $id, array $site, string $path = ''): Temp
 		$policy = new ContentSecurityPolicy();
 		$policy->addAllowedWorkerSrcDomain('*');
 		$policy->addAllowedFrameDomain('*');
+		$policy->addAllowedFrameDomain('blob:');
 		$response->setContentSecurityPolicy($policy);
 
 		return $response;