Help please. Everyone here knows more about computers than I do. So please explain what just happened to me.

I was commenting on CBS St. Louis site, under my second Facebook name. After making a bunch of comments, someone “hijacked” my username and started commenting. Suddenly comments started popping up with my Facebook photo and name, but they weren’t my comments. So someone is screwing with me. Is this anything to be concerned about, or just typical comment section hijinks?

Could the person who started posting as me get access to my personal info? Do I need to start changing passwords and other shit?