Firefox 60.2.0 ESR on Win7 and Win10 - but a lot of versions below had same problem We use a proxy - normally with a .PAC file via System Settings but tested settings within FF with .PAC file or directly entered proxy. It prompts after every launch of FF for Proxy credentials and NEVER shows the "Would you like Firefox to save this login..." For any other site it always offers storing the credetials and it works like it should be. EXCEPT I found one solution: When launching FF Cancel the "Authentication Required" (sometimes 3 to 7 times canceling). Than open any page on the web and authenticate against the proxy - it will show the "Would you like Firefox to save this login..." and it is visible in the password store. Thereafter everything is operational. Another problem: If you ever click on "Never save" for proxy saving credential this proxy site it NOT added to the Exceptions list and cannot be removed and I did not find any way to solve it except removing the Firefox profile. Tested with German and English Version Searched for a solution since a year ever and ever again configured dozens of parameters in about:config which I found on the web. Credentials for every other site are always saved. Users with a old Firefox profiles with saved proxy credential do not have this problem, only new FF profiles - since at least a year possilbly longer.