--- a/dom/canvas/CanvasUtils.cpp
+++ b/dom/canvas/CanvasUtils.cpp
@@ -50,21 +50,34 @@ bool IsImageExtractionAllowed(nsIDocumen
         return true;
     }
 
     // Don't proceed if we don't have a document or JavaScript context.
     if (!aDocument || !aCx) {
         return false;
     }
 
-    // Documents with system principal can always extract canvas data.
     nsPIDOMWindowOuter *win = aDocument->GetWindow();
     nsCOMPtr<nsIScriptObjectPrincipal> sop(do_QueryInterface(win));
-    if (sop && nsContentUtils::IsSystemPrincipal(sop->GetPrincipal())) {
-        return true;
+
+    if (sop) {
+        // Documents with system principal can always extract canvas data.
+        nsIPrincipal *principal = sop->GetPrincipal();
+        if (nsContentUtils::IsSystemPrincipal(principal)) {
+            return true;
+        }
+
+        if (principal) {
+            // Allow extension principals
+            nsAutoString addonId;
+            Unused << NS_WARN_IF(NS_FAILED(principal->GetAddonId(addonId)));
+            if (!addonId.IsEmpty()) {
+                return true;
+            }
+        }
     }
 
     // Always give permission to chrome scripts (e.g. Page Inspector).
     if (nsContentUtils::ThreadsafeIsCallerChrome()) {
         return true;
     }
 
     // Get the document URI and its spec.