Apple has just pushed silent updates to the configuration data for its malware removal tool MRT, and to those for XProtect.
These bring the MRT app to version 1.26, and XProtectPlistConfigData to version 2097.
Added to XProtect’s detection list are OSX.ParticleSmasher.A and OSX.HiddenLotus.A, and existing protection against OSX.Hmining.D has been updated.
You can check whether these updates have 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 for Sierra and High Sierra, available from Downloads above.