We're working on the issue but it's not caused by malware and you cannot open other people's PM's. I've posted in the lounge and the feedback forum to give everyone an update. To reiterate: No one's profile is at risk and there is no way to use another person's account. If you come across the glitch, refreshing once or twice will cause the profile to revert back to your default, clicking on links will have the same effect.
If you've seen something different, PM me with the info and we'll look at it. Please don't post anything about another member's account here in the forum.