gedit is the official text editor of the GNOME desktop environement.
A format string vulnerability exists when opening files with names containing format specifiers.
A specially crafted file with format specifiers in the filename can cause arbitrary code execution.
There are no known workarounds at this time.
All gedit users should upgrade to the latest version:
# emerge --sync
# emerge --ask --oneshot --verbose ">=app-editors/gedit-2.10.3"