My account, with a 3-letter username worth $$$, got hacked yesterday morning probably by this flow, but I did manage to defend it. I think by far the biggest problem with Instagram/FB/Meta auth flow is that 2FA does nothing. You don't need the 2nd factor to disable it, so attackers can just turn it off. Really stupid!

Also, I discovered that many of IG's auth endpoints are just broken. For example you can't change password on web because of CORS, which isn't a transient outage but just a flat out bug.

Edited to add: This is just the cherry on top of years of stupid auth flow at IG. I have received tens of thousands of reset links or codes from IG over the years. There used to be a way to put your account on recovery cooldown for a few weeks but they got rid of even that.