I think I found a security-relevant design problem with Jevents calendars, namely the integration of Google calendars as described here:
https://www.jevents.net/docs/jevents/item/authorisation-icals-and-google-imports
In order to update the calendars, you have to call a URL like so:
https://<YOUR-URL-HERE>/index.php?option=com_jevents&icsid=2&task=icals.reload
First off, instead of calling that URL by a cron task, it would be better to do this with a "Get Request" via the Joomla Task Scheduler (
https://magazine.joomla.org/all-issues/march-2022/get-to-know-the-new-joomla-task-scheduler).
But note that this URL is externally accessible and contains a nearly static "icsid", probably 2 if you only have one calendar. Thus, the URL for a DOS attack is easy to guess.
As there is no authentication on this URL whatsoever, so anyone can call it as often as they like.
In order to fix this, there are four levels of better security for this in ascending order:
1. At least, the icsid should not be sequentially assigned, but random, to obfuscate the URL. This can be achieved by users by changing the icsid in the corresponding database table to a random id.
2. The task or the whole component could be protected by a password or token.
3. If the cron scheme must be kept at all, the job should not be called by accessing a URL, but provided by the component as a PHP script that is only accessible from the host itself. By doing this, a cron job would not call "curl", but PHP with the script path, thereby avoiding an accessible URL.
4. The best way to fix this IMHO is to provide a task for the component that can be activated in the Joomla Task Scheduler and to avoid URLs and cron altogether.
On a side note: There are other "tasks" provided by the component like "day.listevents", which I saw flashing by when I tried this. I did not look into any further, but those may be prone to similar attack vectors as well, as they seem also to be unprotected.