A recent WMF-wide change is now requiring an unwanted manual confirmation when invoking the PURGE action. The change was made because of the multi-datacenter "project, of which one of the requirements is that no database write actions happen on GET requests."
This appears to be the same type of unwanted confirmation behavior that was presented when T136375 was requested to rollback T88044
Screenshots here:
https://commons.wikimedia.org/wiki/File:Mediawiki-bad-purge-20160821-Capture.PNG
https://commons.wikimedia.org/wiki/File:Mediawiki-bad-purge-20160821-Capture-tr.PNG
See also https://en.wikipedia.org/wiki/Wikipedia:Village_pump_(technical)#Purge_links_require_confirmation_step
Expected behavior: Passing action=purge should trigger a page cache purge
Current behavior: A second page is being loaded, manually requiring users with purge access to confirm their request