GHSA-j2r6-r929-v6gf

### Impact
It is possible to schedule/trigger/unschedule existing jobs by having an admin visit the Job Scheduler page through a predictable URL, for example by embedding such an URL in any content as an image.

To reproduce in an XWiki installation, open `<xwiki-host>:/xwiki/bin/view/Scheduler/?do=trigger&which=Scheduler.NotificationEmailDailySender` as a user with admin rights. If there is no error message that indicates the CSRF token is invalid, the installation is vulnerable.

### Patches
The vulnerability has been fixed on XWiki 14.10.19, 15.5.5, and 15.9.

### Workarounds
Modify the Scheduler.WebHome page following this [patch](https://github.com/xwiki/xwiki-platform/commit/f16ca4ef1513f84ce2e685d4a05d689bd3a2ab4c#diff-1e2995eacccbbbdcc4987ff64f46ac74837d166cf9e92920b4a4f8af0f10bd47).

### References
- https://jira.xwiki.org/browse/XWIKI-20851
- https://github.com/xwiki/xwiki-platform/commit/f16ca4ef1513f84ce2e685d4a05d689bd3a2ab4c