User Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Firefox/78.0

Steps to reproduce:

Seting option resistfingerprinting brakes enter to
https://allegro.pl/ site.
After downgrade to Firefox everything works OK.

(In reply to bpiter from comment #0)

User Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Firefox/78.0

Steps to reproduce:

Seting option resistfingerprinting brakes enter to
https://allegro.pl/ site.
After downgrade to Firefox everything works OK.

After downgrade to Firefox 89

Thank you for the report. Something on this site is blocking access because the option is enabled. This is different from the site not working because of the option. I'm going to keep the bug on file because it would be good to understand what the site is using to determine whether or not to block you, but it's likely we won't be able to resolve this issue.

I'll also note that even after disabling RFP and clearing site data I was blocked....

Worksforme with and w/out RFP (vanilla profile, all site data sanitized between tests), can search, browse categories, drilled down into motorcars and found myself a sweet 1985 Acura Integra, all images load .. what is supposed to break?

Assigning a component for it, please feel free to change it if this is not the correct one.