Did you buy a Mac, iOS device or the Apple World Travel Adapter Kit between 2003 and 2010? If you did, chances are that you received a wall plug too. Turns out that the three-prong adapters sold in certain countries during that period can break and cause an electric shock if touched.
https://www.notebookcheck.net/Dangerous-fruit-Apple-recalls-specific-wall-plugs-over-electric-shock-risk.419293.0.html