XWiki Platform's Groovy jobs check the wrong author, allowing remote code execution

XWiki Platform is a generic wiki platform offering runtime services for applications built on top of it. XWiki supports scheduled jobs that contain Groovy scripts. Currently, the job checks the content author of the job for programming right. However, modifying or adding a job script to a document doesn't modify the content author. Together with a CSRF vulnerability in the job scheduler, this can be exploited for remote code execution by an attacker with edit right on the wiki. If the attack is successful, an error log entry with "Job content executed" will be produced. This vulnerability has been patched in XWiki 14.10.9 and 15.4RC1.