Firefox Decrypt is a tool to extract passwords from Firefox profiles.

It can be used to recover passwords from a profile protected by a Master
Password as long as the latter is known.
If a profile is not protected by a Master Password, a password will still be
requested but can be left blank.

This script is written in Python and is compatible with versions 2.6-2.7.

Additionally it requires access to libnss3 which is part of Firefox and
Thunderbird, although depending on system configuration, the script may fail to
locate it there.

Alternatively you can install libnss3 (Debian/Ubuntu) or nss (Arch/Gentoo/...).
libnss3 is part of http://www.mozilla.org/projects/security/pki/nss/