Apple has just released the update to El Capitan, bringing it to OS X 10.11.3, which is available from the Mac App Store. It is accompanied by Security Update 2016-001 for 10.9.5 and 10.10.5.

It includes two rather obscure bug fixes:

• it fixes a problem which prevented some Macs from waking from sleep when connected to some 4K displays
• it fixes a problem when upgrading from Yosemite, which could trash third-party receipts from /var/db/receipts.

Security fixes include:

• a memory corruption issue in the parsing of disk images
• memory corruption issues in IOAcceleratorFamily, IOHIDFamily, IOKit, the kernel, and syslog
• OSA Script scripting libraries could be overridden by a quarantined app.

Installation includes at least one restart. Following that, you may see a worryingly blank black screen for a while: this should be replaced by further evidence of the installation proceeding, and eventually you will be logged back in automatically, without having to enter your password.

iOS 9.2.1 has also been released.