Check your iframes
The iframe checker is now included internally and can also check once every day all of your iframes! Since version 2020 this is done in parallel AND also checks iframe which are NOT advanced iframe iframes! So can monitor already existing iframes if they are still can be included! Everyone who uses iframes should use this features to make sure that users don’t see blank pages suddenly.
Standalone version included!
You can use this plugin not only in WordPress but any php page where you can insert a few lines of code!