This advisory also applies to the corresponding versions of Kubuntu, Edubuntu, and Xubuntu.
Details follow:
It was discovered that the poppler PDF library did not correctly handle certain malformed embedded fonts. If a user or an automated system were tricked into opening a malicious PDF, a remote attacker could execute arbitrary code with user privileges.
Solution: The problem can be corrected by upgrading your system to the following package versions:
Ubuntu 6.06 LTS: libpoppler1 0.5.1-0ubuntu7.4
Ubuntu 6.10: libpoppler1 0.5.4-0ubuntu4.4
Ubuntu 7.04: libpoppler1 0.5.4-0ubuntu8.3
Ubuntu 7.10: libpoppler2 0.6-0ubuntu2.2
After a standard system upgrade you need to restart your session to effect the necessary changes.