This plugin BROKE my theme preview! I've been beating myself up for hours -- literally overnight -- trying to figure out why I can't preview my installed themes and then ACTIVATE them. I've been searching and reading Codex, Docs, Forums, online searches -- everything.
I was ready to reinstall WordPress -- which wouldn't have done a darn bit of good and/or delete my tables which would have been really bad.
Once I thought to look over my plugins again -- after many, many other times, it finally hit me that this could be the culprit. I deactivated this plugin and VOILA -- I can preview and activate a new theme!! It's going bye-bye for sure. I'll look for another plugin to prevent site theft through frames.
We learn through our mistakes, but this is one I would rather have avoided.