Here's a video of what happened (recreated after I got the original forum account back on MTG):
So basically I changed my password and I didn't enter the new one before hitting Enter (in the video, I just clicked 'Save Changes') and it still managed to change the password. I originally posted the bug report here (on the MTG forums) and they just told me to post it here. So I did. (Don't know if you can maybe get more details from the other report, but that's basically the original report that I made.)
EDIT: With my first account on the MTG forums, I lost my account by doing what I did in the video. After i got that account back, I made the video with my second account.
The forgot password option didn't work with my original account, but then worked with my second account.