You know, if people would just do this before installing stuff from dangerous repositories, all would be well

1) make a backup using that wonderful backup app
2) install the "bork device app of the day"
3) bork bork bork
4) reflash to whatever firmware version you were running before
5) restore from backup

Hey, look - you're exactly where you were before!

Before I hear you whine "that's too much work" - stay out of the not-for-general-release repositories if its too much work.