diff --git a/src-tauri/src/cloud_review.rs b/src-tauri/src/cloud_review.rs
index 349a75ee1..15ea9db7b 100644
--- a/src-tauri/src/cloud_review.rs
+++ b/src-tauri/src/cloud_review.rs
@@ -279,6 +279,13 @@ fn secure_decision_directory(path: &Path) -> Result<(), String> {
     if !metadata.is_dir() || metadata.file_type().is_symlink() {
         return Err("cloud-review-directory-unsafe".into());
     }
+    #[cfg(unix)]
+    {
+        use std::os::unix::fs::PermissionsExt;
+        if metadata.permissions().mode() & 0o022 != 0 {
+            return Err("cloud-review-directory-writable-by-others".into());
+        }
+    }
     Ok(())
 }
 
diff --git a/src-tauri/tests/cloud_review_directory_authority.rs b/src-tauri/tests/cloud_review_directory_authority.rs
new file mode 100644
index 000000000..b46ab7719
--- /dev/null
+++ b/src-tauri/tests/cloud_review_directory_authority.rs
@@ -0,0 +1,19 @@
+#[cfg(unix)]
+#[test]
+fn shared_writable_cloud_review_directory_fails_closed() {
+    use disksage_lib::cloud_review::load_latest_decisions;
+    use std::os::unix::fs::PermissionsExt;
+
+    let directory = tempfile::tempdir().expect("temporary review directory");
+    let mut permissions = std::fs::metadata(directory.path())
+        .expect("review directory metadata")
+        .permissions();
+    permissions.set_mode(0o777);
+    std::fs::set_permissions(directory.path(), permissions)
+        .expect("make review directory shared-writable for regression");
+
+    let error = load_latest_decisions(directory.path())
+        .expect_err("shared-writable review authority must fail closed");
+
+    assert_eq!(error, "cloud-review-directory-writable-by-others");
+}