Apple has just pushed an update to its malware removal tool, MRT, for macOS, bringing its version number to 1.38. The last update brought version 1.35 nearly six months ago (19 June 2018), and Apple seems never to have released versions 1.36 or 1.37.
Apple doesn’t provide any information on what changes this update brings. As it now obfuscates the names of malware which it can detect and remove, it appears impossible to correlate changed strings in the app with any malware known outside Apple.
You can check whether this update has been installed by opening System Information via About This Mac, and selecting the Installations item under Software.
A full listing of security data file versions is given by LockRattler and SystHist for El Capitan, Sierra, High Sierra and Mojave, available from Downloads above. If your Mac has not yet installed this update, you can force an update using LockRattler, or at the command line.
I have updated the reference pages here which are accessed directly from LockRattler 4.2 and later using its Check blog button.
For those using the latest version of LockRattler (4.18), you should see its new red text feature at work: when you have installed the update, click on the Refresh button, and the installation details will be updated and displayed in red. If you then close LockRattler and open it again, you’ll see the MRT version number in red, indicating its recent update.
I maintain lists of the current versions of security data files for Mojave on this page, High Sierra on this page, Sierra on this page, and El Capitan on this page.
(Thanks to Al for alerting me to this, and for confirming that Apple’s new names don’t make any sense to anyone else.)