Apache Tiles: Unvalidated input may lead to path traversal and XXE

** UNSUPPORTED WHEN ASSIGNED ** The value set as the DefaultLocaleResolver.LOCALE_KEY attribute on the session was not validated while resolving XML definition files, leading to possible path traversal and eventually SSRF/XXE when passing user-controlled data to this key. Passing user-controlled data to this key may be relatively common, as it was also used like that to set the language in the 'tiles-test' application shipped with Tiles. This issue affects Apache Tiles from version 2 onwards. NOTE: This vulnerability only affects products that are no longer supported by the maintainer.