Tony StillApple has released software updates for pretty much all of its products. This includes the Catalina 10.15.5 (Supplemental), related updates for some older macOS versions, iPadOS 13.5.1, same for iOS, watchOS 6.2.6 and probably others.
It's important that the updates are applied promptly because the consequences are potentially severe.
The fix is for a kernel bug that allows arbitrary code execution with kernel privileges (ie an attacker can do anything with full access to your machine). It's already in use by the jailbreak community so the malware writers will quickly have access to it.