diff --git a/engine/src/flutter/.github/workflows/mirror.yml b/engine/src/flutter/.github/workflows/mirror.yml
index f8a5e788970..c5e20e9cf3f 100644
--- a/engine/src/flutter/.github/workflows/mirror.yml
+++ b/engine/src/flutter/.github/workflows/mirror.yml
@@ -8,6 +8,9 @@ on:
     branches:
       - 'main'
 
+# Declare default permissions as read only.
+permissions: read-all
+
 jobs:
   mirror_job:
     permissions: