OSX Window server vulnerabilities on catalina
Apple does not use X11 or XQuartz in any way. It's an entirely third-party app, created to run the X windows environment inside Apple's own Quartz graphics system.
The last build of XQuartz was released in 2016. Most people only use it to run particular software, like FontForge. They are unlikely to use it as a general computing environment.
I suspect that the security problems you mention only exist within the X environment, rather than bleeding out into MacOS's own window server. Apple has introduced all sorts of security features to restrict applications' operations and scope of influence, so I would be very surprised if these flaws existed.