I did a simple search of each of those Mozilla. xxx and they have forums that talk about them but nothing saying it's coming from Firefox itself. Sounds more like false positive on those search forum for unbuntu that I read.

I am using Tor nowadays because I get a trojan horse or other possible threats, every time using Firefox. I use ClamTk on my HP computer with Linux Mint 21.1 installed. These are the 3 files that usually turn up after a full scan with ClamTk: Mozilla Firefox PUA.Win.Trojan.Xored-1 Mozilla Firefox PUA.Html.Exploit.CVE_2012_ Mozilla Firefox PUA.win.Exploit.CVE_2012_none I found out when my website turned out to be hacked, so I installed the ClamTk virus scanner. Just to let you know so you might find a solution. Thanks, Frank

Where were these being found?. based on some searching these are mainly found in the Cache by Clam so if that is the case then they are harmless. Whether there is something of a trojan or malware etc in Cache or not, it is harmless while there unless you went in that folder and tried to say run that file yourself. It is harmless if left alone and will be overwritten as stuff gets added to Cache or deleted when you clear cache anyways.

Old article but still relevant. https://support.mozilla.org/en-US/kb/Firefox+cache+file+was+infected+with+a+virus

PUA means "potential unwanted application". PUA are not virusses, those are claims by clamav that there is an application they consider "unwanted" because that file or extension have been proven to be abused in Windows