uMatrix iframes not scrollable

[BlueMax]

Hallo,
iframes of uMatrix are not detected as scrollable area.

Steps To Reproduce

1. Go to uMatrix settings (click addon symbol -> top black bar).
2. Make sure 'hide blocked elements' is not enabled.
3. Visit https://fastaddons.com
4. Scroll down to the (blocked) youtube iframe.
5. The gray checkered area is not scrollable (see pic below) and you have to move the mouse cursor outside the iframe first to be able to scroll again.

Device info:

• Arch Linux 5.8.10
• Firefox 80.0.1
• ScrollAnywhere 8.4

[fastaddons]

So, this will be hard. It seems that the uMatrix will replace (or clear?) the iframe and somehow my extension won't be running inside. That's unexpected behavior since my extension should be executed in all frames.
The same problem should however affect also other iframes with blocked javascript even without the uMatrix. Such iframes are not very common on the web, but still possible.

The only solution I can think of is identify all frames where my script is not running and "somehow" block them.

However there is a good chance it will not be possible. All mouse events inside iframe are captured by iframe and parent window doesn't see them. All I could do is block all interactions with the iframe but then user will not be able to interact with iframe at all, which is not good because in this case the link inside wouldn't be clickable anymore...

I will investigate this further before releasing new version.