X.Org is an open source implementation of the X Window System. It providesthe basic low-level functionality that full-fledged graphical userinterfaces are designed upon.A flaw was found in the way the X.Org server handled lock files. A localuser with access to the system console could use this flaw to determine theexistence of a file in a directory not accessible to the user, via asymbolic link attack. (CVE-2011-4028)Red Hat would like to thank the researcher with the nickname vladz forreporting this issue.This update also fixes the following bugs:All users of xorg-x11-server are advised to upgrade to these updatedpackages, which correct these issues. All running X.Org server instancesmust be restarted for this update to take effect.