Since upgrading Firefox on two platforms, I have noticed a couple of sites not working well with it. '''CareerBuilder.Com''': When I want to upload new documents, it does not happen. I click on the button and... nothing. It works fine in MS Edge. If instead of clicking on the button, if I copy the link the button represents and paste it in the URL dialogue, it works. '''Recalls.Mopar.Com''': It provides a web form to enter an auto's VIN. in that dialogue web form box is the word "VIN". However it remains there and as I type the first characters of the VIN, the characters are partially obfuscated in the dialogue box by competing text, one on top of the other. After the full VIN is entered, I never get results. When I use MS Edge, the word VIN is above the web form entry box and it does not partially obfuscate the characters and when completed, results come within seconds. Firefox Cookie Handling: There are certain malvertising sites I manually deletes cookies for. in the past versions, no problems. With v91, there are problems. In the past when I performed this function on one such site, it had two cookies according to the Cookies and Site Data data manger. With v91, there is now only one. In the past when I have deleted those cookies, the size of the Cookie Cache would not change. Now when I choose Manage Data, the size can change dramatically. Just now I did it and the Cookie Cache was ~65MB. I deleted the ONE cookie and the cache size decreased to ~42MB. But that is not all, when I visit some other sites that store configurations in a cookie, the configurations are gone and I have to reset said configurations. For example on a particular Web Forum using Invision [ IPS Community Suite version 4.6.5.1 ], Sub-Forums may be expanded or collapsed. I choose to collapse some sub-forums. That setting is stored in a cookie and exists across sessions and time. However, in FF v91, once I delete that ONE non-affiliated Cookie, that web forum's choice of collapsed sub-forums is lost. I have repeated this test numerous times and it is reproducible.