Hi, your Firefox sent this self-identification to the forum:

User Agent:

Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:103.0) Gecko/20100101 Firefox/103.0 Trailer/91.3.2422.23

That last part is not normal. If this is old junk in your Firefox settings, the steps in this article will help you clear it: How to reset the default user agent on Firefox.

Unfortunately, when I searched for more information on "Trailer", I didn't find any results about what program is adding it. However, it has been observed with Chrome, too, so I think it is an external program that is intercepting your browsing. This could be "innocent" software like your security software or something less wholesome (but usually malware doesn't leave a big red flag like that).

One program mentioned in past threads that adds weird stuff to your user agent is Avast AntiTrack / AVG AntiTrack.

The poster in this thread https://support.mozilla.org/en-US/questions/1385639 had a similar issue with the User Agent

The OP said "I found the problem: when I renewed AVG recently, it came bundled with something called Kamo. I had to add my bank's website to Kamo's list of "Allowed sites", and then it worked fine."