There is an Android app that simply let's you generate the default WPA key for a Verizon, D-Link, Thompson, Speedtouch and Sitecom routers. If you download it and install it on your phone, you can often connect to WPA protected routers as most of them are using the default WPA key. I've tested it on multiple routers already. The security breach is even worse if you are also able to login to the router admin.
So please change your default WPA key. I would even recommend to make it something you are able to remember. A long sentence with some numbers added could help. Like a sentence of a song with your postal code and birthday. E.g. yellowsubmarine123401011900
If you would like to test your own network / WPA key, you can get the Android app here:
Here you can also find a list with affected routers...