Clicking the "abort" link in an externaldebsign task gives HTTP 405

When an externaldebsign task is running, it gives a nice help text:

Run debusine provide-signature NNN to sign this request. If you do not want to sign it, you can abort it instead.

In this text, the word "abort" is a link. Clicking it results in HTTP status 405. At the same time, there is the abort button (form) in the right column and that just works. Aborting a work request requires a POST request (e.g. to avoid CSRF) and therefore a simple <a href=... is not going to work.