Scrollbars appear in click2load.html

[ghcsd]

Prerequisites

• I verified that this is not a filter issue (MUST be reported at filter issue tracker)
• This is not a support issue or a question
• I performed a cursory search of the issue tracker to avoid opening a duplicate issue
• The issue is not present after wholly disabling uBlock Origin ("uBO") in the browser
• I checked the documentation to understand that the issue I report is not a normal behavior

I tried to reproduce the issue when...

• uBO is the only extension
• uBO with default lists/settings
• using a new, unmodified browser profile

Description

In Firefox, scrollbars always appear in click2load.html

A specific URL where the issue occurs

https://developer.mozilla.org/en-US/docs/Web/Guide/Audio_and_video_manipulation#video_and_webgl

Steps to Reproduce

1. Add *$frame,redirect=click2load.html to My filters
2. Open https://developer.mozilla.org/en-US/docs/Web/Guide/Audio_and_video_manipulation#video_and_webgl.

Expected behavior

Scrollbars should not appear in the placeholder document.

Actual behavior

uBlock Origin version

uBlock Origin 1.39.3rc1

Browser name and version

Firefox 95.0.2

Operating System and version

Windows 10

[ghcsd]

Using

body {
  width: 100vw;
  height: 100vh;
}

instead of the inline style can solve this issue.
ghcsd/uBlock@e344b64

[gwarser]

[gwarser]

High DPI monitor? System/browser scaling?

[ghcsd]

High DPI monitor? System/browser scaling?

Yes, It is easier to reproduce when Firefox browser is not the default zoom level (eg. 110%).
You can zoom in/out (Ctrl - +/-) and refresh the page to reproduce the issue.

[ghcsd]

Adding the following CSS code to userContent.css can temporarily fix this issue.

@-moz-document regexp("moz-extension://[^/]+/web_accessible_resources/click2load\.html.+"){
  #ublock0-clicktoload > body{
    width: 100vw !important;
    height: 100vh !important;
  }
}