It was reported that SLiM versions prior to 1.3.1 assigned logged-in users a predefined PATH which included './', which could allow for unintentional code execution. This was corrected in upstream 1.3.2 .
Fedora has had the slim-1.3.1-curdir.patch included which corrects the default configuration file, however the upstream fix also includes changes to the built-in defaults (used in the absence of a configuration file). So unless the configuration file is missing, Fedora releases are not vulnerable to this.
It's not necessary to provide updates to released versions of Fedora, but it would be good to upgrade rawhide to 1.3.2 to have the full fix.
Created slim tracking bugs for this issue
Affects: fedora-rawhide [bug 625944]