As mentioned in this new advisory on the Secunia website, the Slackware linux group has posted their latest updates to their PHP package (in light of the released of PHP 5.2.4).

Slackware has issued an update for php. This fixes a weakness and some vulnerabilities, where some have unknown impacts and others can be exploited by malicious users and malicious, local users to bypass certain security restrictions.

The update is marked as "moderately critical" so it's recommended that you update as soon as possible. The packages can be downloaded from the Slackware website (from the FTP sites they link to in the original advisory).