OS X 10.11.4, the fourth update to El Capitan since its September debut, addressed 56 vulnerabilities. Apple also issued less sweeping updates to OS X Yosemite and OS X Mavericks, the 2014 and 2013 editions, respectively. Apple stopped patching Mavericks’ predecessor, 2012’s OS X Mountain Lion last year, as part of its practice to support only the OS X editions designated as “n” and “n-1″ The update can be downloaded from the Mac App Store’s Updates section to systems running those editions.”]