All CF shops are urged to install this update immediately, to implement new protections against a known attack happening in the wild. It's identified in the associated Adobe Product Security Bulletin, APSB19-14, as a priority 1 critical vulnerability.
I will add that I can vouch personally for the significance of the vulnerability, as I reported it to the Adobe Product Security Incident Response Team (PSIRT), and I proposed the fix which was implemented. (I also know what was done specifically to perpetrate the attack, and the very negative consequences of what happened once the server of a client of mine was attacked. You don't want this to happen to you.) I plan to share much more in a part 2 post (now posted, but do see below for the context it builds upon).
(In the meantime, I have tweaked this part 1 since originally posting it, to share more here.)