cgit contains a flaw related to syntax-highlighting.sh. The issue is triggered when quotations are purposely left out of an argument, which may allow a remote attacker to inject arbitrary commands via an argument passed to the highlight command.
Currently, there are no known workarounds or upgrades to correct this issue. However, a patch has been committed to the CVS/GIT repository that addresses this vulnerability. Until it is incorporated into the next release of the software, manually patching an existing installation is the only known available solution. Check the vendor advisory or solution URL in the references section.