don't attach to hidden forms

extension/foreground.js

@@ -128,6 +128,13 @@
   }
 
   function attachLoginFormHighlight(info) {
+    if (
+      info.form.offsetParent === null ||
+      window.getComputedStyle(info.form).display === 'none'
+    ) {
+      return;
+    }
+
     successfulAttachment = true;
     const autoFillContainer = document.createElement('div');
     Object.assign(autoFillContainer.style, {
@@ -174,7 +181,7 @@
       background: 'transparent',
       fontWeight: 'bold',
       fontSize: '12px',
-      pointerEvents: 'all'
+      pointerEvents: 'all',
     });
     autoFillContainer.appendChild(close);