Anyone else has the same issue with XHR on Firefox, where it sends shitload of requests and then does something?

Testing the same code on Chromium stuff works just fine, only one request and calls another method. Firefox does free DDOS

no? you sure it isnt an Options request getting in some bad/wrong loop?

@azuredivay Checked my code, seems fine on Chrome. Same thing happens on Microsoft login page.

Running ffox 120 on Windows

How vague do you like your problem description?
@ttomovcik: yes

At this point I'd guess it's probably a silly oversight, never encountered it and been using Firefox for years, maybe an extension? Or some feature that is not supported/ API that follows an earlier spec in different browsers..

@ttomovcik I was scared to update mine to 120 coz of you -_-
updated anyway and it worked the same

If it's specific to your website, open a BugZilla ticket

FF isnt really known to be the most stable so it's possible it's a bug particular to your implementation