Exporting the List of installed Windows Security Updates on the Server
Recently found another method that doesn't require 3rd party software using wmic; just type: wmic qfe from the command line. The default output gives really long lines, so you might be better off redirecting to a file and viewing it in your favorite text editor.
Variations on a theme include:
wmic qfe list full
wmic qfe get HotfixID,ServicePackInEffect,InstallDate,InstalledBy,InstalledOn
wmic qfe where "HotfixID = 'KB973687'"
wmic qfe where "HotfixID = 'KB973687'" get HotfixID, InstallDate, InstalledBy, InstalledOn