This looks like a video driver issue. Since xp is no longer supported for firefox you may want to try on at least Windows 7.

https://www.mozilla.org/en-US/firefox/53.0.3/system-requirements/

You should also check out Firefox; Extended Support Release {web link} ESR Notes System Requirements

Well that's odd. Weird there's no setting for whatever was introduced that blurs the whole user interface.

can you please update to firefox 52.2.0 and then go to the firefox menu ≡ > help ? > troubleshooting information, copy the contents of that page and paste them here into a reply on the forum? this might give us more of a clue what is going on...

thanks

51.0 (32-bit) raw https://pastebin.com/9Zw7HNX2 text https://pastebin.com/aaQYb8kq

52.0.1 (32-bit) raw https://pastebin.com/xZNpTs5C text https://pastebin.com/4MbQ5zVB

the actual reason I'm posting is that this affects the TorBrowser too.

as i've said, can you please try with the most recent 52.2.0 which may contain a fix for this issue (bug 1345222).

in case it doesn't help try the following: enter about:config into the firefox address bar (confirm the info message in case it shows up) & search for the preference named gfx.content.azure.backends. adjust it by removing the skia bit from the pref.

philipp said

as i've said, can you please try with the most recent 52.2.0 which may contain a fix for this issue (bug 1345222).

Oh I'm truly sorry for that.

But removing skia *did* help. Thank you very much for this. Should I still paste a Troubleshoot output?

no, if you could solve it & are happy that way, that'll be a long-term fix :-)