User Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:85.0) Gecko/20100101 Firefox/85.0

Steps to reproduce:

I have recently found out that when I type in web editors or move the mouse over certain pages, e.g. youtube, Firefox malfunctions with broken display. This becomes annoying. I will attach a video of this behavior and a screenshot of a youtube video. The problem doesn't exist with other browsers. I tried to uninstall firefox and delete the folders in appdata folder and then reinstalled it again. But still see the same behavior.

Firefox version: 85.0.2 (64 bit)
Windows 10 64 bit, version 1909

The Bugbug bot thinks this bug should belong to the 'Core::Graphics' component, and is moving the bug to that component. Please revert this change in case you think the bot is wrong.

The problem seems to hit a driver bug.
nt_mahmood, can you attach about:support to this bug? Thank you!

Driver of Intel 4600 is very old, then WebRender native compositor might not work well.

"driverVersion": "20.19.15.4416",
"driverDate": "3-23-2016",

nt_mahmood, thank you for the info! Can you test for disabling WebRender native compositor?
It could be disabled by setting pref "gfx.webrender.compositor" to false at about:config. Then restart Firefox.

Thanks for the tip. I will try that and see if FF remains stable or not.
Meanwhile, as I check my laptop driver page [1], I see that the latest HD 4600 driver is for 2016 and the version is lower than what you found 10.18.15.4416 31 May 2016

On the other hand, in the Intel driver page [2], I see some older versions than mine in spite of the release date!
15.40.48.5171 2/5/2021.
and the driver assistant application says no update available.

So, I am confused with the driver version that I have. But that is not a big deal. I will test with the option you mentioned and check it is persistent or not.

[1] https://pcsupport.lenovo.com/be/en/products/laptops-and-netbooks/thinkpad-edge-laptops/thinkpad-edge-e440/20c5/20c5a0l300/pf064c31/downloads/driver-list/component?name=Display%20and%20Video%20Graphics
[2] https://downloadcenter.intel.com/product/81496/Intel-HD-Graphics-4600

@Sotaro
It seems that the trick you mentioned fixed the issue. I no longer see such annoying behavior.
Although you mentioned the driver is old, I hope that FF developers find a way to automatically check and fix that in future releases.

https://downloadcenter.intel.com/download/30196/Intel-Graphics-Driver-for-Windows-15-40-
https://downloadmirror.intel.com/30196/eng/ReadMe64.txt

Driver Version: 20.19.15.5171
The driver on Intel's page is actually much newer than your outdated driver.

This has always been a terrible problem with older Intel driver versions, the version on the driver download page doesn't match the actual version number reported in Device Manager or Intel's own control panel. Intel Gen9 and later GPU generations uses a much saner version number that matches what Device Manager reports.

https://www.intel.com/content/www/us/en/support/articles/000005654/graphics.html

"100 & Newer Drivers
The Intel® Graphics Driver version schema used in Download Center will change with the Windows® 10 April 2018 Update release to provide better scaling and support for our driver build process, and at the same time match the drivers naming convention used in Windows*."

"15.65 & Older Drivers
Download Center also hosts graphics drivers that use a naming schema to define driver versions that may not match 1-to-1 the operating system's own driver convention as detailed in the previous tables."

Unfortunately, when I execute win64_15.40.5171.exe it says that the driver is not validated for this computer, despite the fact that my processor Core™ i5-4210M is listed in the page.
https://downloadcenter.intel.com/product/81012/Intel-Core-i5-4210M-Processor-3M-Cache-up-to-3-20-GHz-

Never mind! I will follow this bug thread to disable the web render compositor in the future.
Thanks for solving that. I appreciate.