The most recent update was an emergency fix for an in-the-wild exploit that was being used against both Windows and Mac users. Presumably (and we don’t know, because this is the first time Apple has done this for Flash, though it did something similar for Java back in January 2013), the amount of time you get before Apple drops the hammer will vary depending on the apparent risk.
Once Apple thinks you’ve had enough time to get around to updating Flash (two days in the case of the most recent update), it issues a new Xprotect signature that pretty much forces your hand. OS X users received an automatic update via Apple’s basic threat protection system, Xprotect, to lock old Flash player plugins out of your browser. Last week, Apple showed that it is getting more serious about security by turning all strict about the version of Flash you’re allowed to use in Safari.
