Apple has announced a recall of defective iPhone charging adapters after reports they could overheat and combust, causing possible injuries or fire. The only charger affected by this recall is for European outlets. Here's part of the statement from Apple's official release:
Apple has determined that, in rare cases, the Apple 5W European USB power adapter may overheat and pose a safety risk. This adapter came with iPhone 3GS, iPhone 4 and iPhone 4S models shipped from October 2009 to September 2012 in the countries listed below. It was also sold as a standalone accessory.
Apple has set up an exchange program. If you own a defective charger, you'll be able to take it into an Apple store and get a new, safe model for free. Apple doesn't want to refer to this a recall, preferring the term "exchange program," but when you encourage people to bring back a defective product and swap it out for one that works, it's pretty much a recall.
If you have a charger with the number A1300, you need to get the new one with A1400:
Here are the countries in which this adapter was sold: