Seen in https://doc.owncloud.com/server/next/admin_manual/installation/quick_guides/ubuntu_20_04.html#set-up-a-cron-job
User tries to highlight the code with the mouse, Everything except the > character can be highlighted.

When the result is pasted, the command fails with an error message of
bash: /var/spool/cron/crontabs/www-data: Permission denied
Something is rotten in the state of Antora.
Backports needed.
FYI: @emma1382 this is what happened to you :-)