I believe that Optifines website has a leak

I was going on to check and see why I couldn't see my optifine donor cape and when I logged into my mojang account through their site, I was surprised to see that someone who I didn't know had transferred my cape to their account. No big deal though. Sure enough, 21 minutes later I get an email from Mojang saying that they suspected suspicious activity on my account and that my password had been changed. Naturally I go and change it again, then to test to see if optifine was the leak, went and re-logged into my account on their website and sure enough my password was changed again not too long after this. Considering that Optifine has a pretty big reputation around the community, I thought that it was worth bringing to peoples attention.

EDIT 1: Fortunately, and unfortunately, I don't have any malware on my computer. I'm gonna redo the process and take screenshots through it to show what is happening.