Apple has just pushed two updates, to the data files used by XProtect, bringing its version number to 2139 dated 4 February 2021, and to its malware removal tool MRT, bringing it to version 1.73, also dated 4 February 2021.
Apple doesn’t release information about what these updates add or change, and now obfuscates the identities of malware detected by XProtect using internal code names.
Changes found in the XProtect Yara definitions include amendments to the those for MACOS.de444f2, MACOS.b70290c and MACOS.22d71e9. There don’t appear to be any additions to the list of malware detected.
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 SilentKnight, LockRattler and SystHist for El Capitan, Sierra, High Sierra, Mojave, Catalina and Big Sur, available from their product page. If your Mac has not yet installed this update, you can force an update using SilentKnight, 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.
I maintain lists of the current versions of security data files for Big Sur on this page, Catalina on this page, Mojave on this page, High Sierra on this page, Sierra on this page, and El Capitan on this page.