Apple is recalling some wall plug adapters (duckheads) that were shipped with products between 2003 and 2015…
https://www.apple.com/au/support/ac-wallplug-adapter/
Affected adapter:
Unaffected adapter:
The affected adapters have a 4, 5, or no characters inside the slot, whereas the unaffected adapters will have the country or region code.
Serial numbers will need to be verified before Apple provides you with a replacement.