Also posted this in r/Streaming:
Twice I have tried logging into my shudder account on Firefox and was randomly logged into random peoples accounts. This only happened in Firefox. I had a friend do the same thing on his computer (he does not have a shudder account and lives in another state so obviously different internet network). It did not work on Chrome but he was able to simple access content on some random person’s account on Shudder having never visited the website today. I do not know where or how to report such a security breach.