hi, thanks for reporting this. we are currently looking into this issue in https://bugzilla.mozilla.org/show_bug.cgi?id=1435472

so far it appears to be an issue that only affects users who have turned off cleartype font rendering within their windows settings. so a workaround for the moment would either be to turn cleartype back on or disabling hardware acceleration in firefox: Firefox's performance settings

Hi, sorry to hear that. Could you please from the 3 Bar Menu go to Options then down to Performance and turn off Use Hardware Acceleration and see if the problem is still there.

Yes, this fixed the problem. But will this affect me watching videos or something that requires Hardware acceleration to boost performance?

Will there be a fix soon so I can turn back hardware acceleration?

so far it appears to be an issue that only affects users who have turned off cleartype font rendering within their windows settings

You can try turn on the cleartype fonts again and see if that stops the need for Hardware Acceleration to be turned off.

Yes it could effect watching or viewing or just on the web, you would see artifacts and or screen tearing if there was a issue. Pixels.