Super frustrating the AI Chatbots are infecting my Firefox browser now. It looks like malware and pretty much acts like it since it cannot be disabled from the sidebar outside of closing this window. I like vertical tabs, but they require so many other options by default. Even more frustrating that the URL goes to a chrome browser link: chrome://browser/content/genai/chat.html
Alarms very heightened.
That's the anti-fingerprinting tampering with HTML canvas to prevent it from being used to fingerprint your browser. Anti-fingerprinting is awesome, but as you've discovered, does not play nice with many (legitimate) uses. Unfortunately, the only solution is to turn fingerprinting off. There are a couple ways of doing this. The first way is to just disable the whole fucking thing from the settings, but Librewolf makes strong arguments for leaving it on, and those are pretty justified. Another option is to have a non-fingerprint-protection profile you can open sites in when you have problems in your default configuration for sites you generally trust. That can get tedious. You can also use an addon for canvas-blocking instead, there are quite a few, including CanvasBlocker.
Basically, once you turn off the resist-fingerprinting (RFP) LibreWolf is still very privacy-oriented, but generally just works flawlessly. The RFP defaults to on for a reason, but it can also be disabled for a reason too. If you don't want it, you don't have to use it. It's just a default. And it's a good default.
What is it called in the settings?
They have a FAQ for it that explains better than I can