3 answers
Hello,
This is a specific Firefox error with many potential causes, but the most common ones are the disruptive intervention of a VPN or third-party security software, see here:
https://kinsta.com/fr/base-de-connaissances/erreur-pr-end-of-file/
Hello.
This could also be due to an infection, but it's quite rare https://www.malekal.com/mozilla-firefox-pr-end-of-file-error/
To check if it's an infection:
Download FRST, once downloaded save it to your desktop, then right-click on FRST and select Run as administrator you will see this:

Wait until the message the tool is ready to run appears then click on Scan
Warning, wait for the messages indicating that the scan is completed to appear.

At the end of the scan, you will have two text files on the desktop FRST and Addition.

Then send the FRST and ADDITION reports to https://pjjoint.malekal.com/ then provide the two links generated by https://pjjoint.malekal.com/ in your response.
bazfile
Moderator/Security Contributor.
a hello, a response, a thank you are always appreciated.