Apple has updated its Flash Player blacklist again, this time blocking versions lower than 18.104.22.1686 and 22.214.171.1244. The move follows a zero-day exploit currently targeting Windows PCs that could also potentially go after Macs, too.
Apple blocks older Flash Player versions following zero-day exploit
Adobe released a Flash Player update for Mac and Windows last week to address a major security flaw that hackers were actively using to push malicious payloads to Windows PCs. Attackers were loading ad fraud malware onto victim's PCs through websites they had compromised.
Last week's Flash 126.96.36.1997 update addressed one zero-day exploit while leaving a second unpatched. Adobe acknowledged the issue and promised a second emergency update would be coming out this week. That update, 188.8.131.526, hit today, so Apple chose to disable older versions from running on Mac computers.
If you're still running earlier unpatched Flash Player versions, Safari will display a dialog letting you know it's time to update when you try to view Flash content. You can also check to see if you're running the latest Flash Player version at Adobe's Flash website.
Alternately, if you don't need Flash Player, you can remove it if at some point it was installed.