Vulnerability researcher here. This vulnerability was patch-gapped before it was disclosed.

When the patch went out 9 days ago [1], many vulnerability researchers were able to look at it and identify the root cause within minutes. Exploits started going out over a week ago before it was publicly disclosed and the CVE was released. Good security orgs that can hire skilled vulnerability researchers started patching on December 6th/7th/8th. All the chaos started on December 9th when people started leaking the poc on twitter.

The same thing happens to google chrome when they release a patch for a security vulnerability. Very skilled researchers can produce a POC and exploit given the patch alone [2]

[1] https://github.com/apache/logging-log4j2/commit/d82b47c

[2] https://blog.exodusintel.com/2019/09/09/patch-gapping-chrome...