That's unlikely, can you be more specific about the update release date and the version. I also believe that an update in browser wouldn't erase files, data stored on the physical disk(hdd or ssd or Nvme). However your browser stored information can/can't change. If it has it could be any malicious software mistakenly downloaded from a third party site. I would also like to follow up on the issue.

Did you already try doing a normal shutdown and restart of Windows? That can help with releasing locked files and resolving problems with user privileges.

After restarting the computer,

You may have ad/mal-ware. Further information can be found in this article; https://support.mozilla.org/en-US/kb/troubleshoot-firefox-issues-caused-malware?cache=no

Run most or all of the listed free to use malware scanners. Each works differently. If one program misses something, another may pick it up.