I am using qBittorrent v4.1.5 and WebUI has been working perfectly for years. I haven't made any changes to the settings or updated the program recently. Today, trying to access it via Chrome results in an "invalid username or password" error. But if I visit the same URL in incognito mode or in Firefox and use the same username/password combination, I am able to log in successfully.
I have attempted changing the port, username, and password, disabling and re-enabling Web UI, exiting and relaunching qBittorrent, and turning off any ad blockers on the URL and nothing has fixed it. This really doesn't make sense.