“Volexity was subsequently able to recreate that exploit and identify a zero-day vulnerability impacting fully up-to-date versions of Confluence Server.”
Attackers dropped a China Chopper webshell on fully patched Confluence servers over Memorial Day weekend. Volexity reported it on May 31. When the post went up there was no patch and no workaround, only an advisory. Every company running its wiki on the open internet was told to wait. The fix landed a day later.