Description
XWiki Platform is a generic wiki platform offering runtime services for applications built on top of it. Starting with version 8.3-rc-1 and prior to versions 12.10.3 and 14.0, one can ask for any file located in the classloader using the template API and a path with ".." in it. The issue is patched in versions 14.0 and 13.10.3. There is no easy workaround for this issue.
Remediation
References
https://github.com/xwiki/xwiki-platform/commit/4917c8f355717bb636d763844528b1fe0f95e8e2
https://github.com/xwiki/xwiki-platform/security/advisories/GHSA-9qrp-h7fw-42hg
https://jira.xwiki.org/browse/XWIKI-19349