Identify the underlying browser

What is the web browser that Songbird utilizes? It seems like this should be in the About Songbird section. I also tried looking through the Songbird site, and I googled for the answer to no avail.

I serendipitously discovered the answer at this address: <http://getsatisfaction.com/songbird/t...>

I only mention it because I was reluctant to use Songbird is because I wasn't sure if it used the latest, most secure Firefox code.