Microsoft's light sprinkling of just three bulletins as part of its November Patch Tuesday contains a patch to address a critical hole that is particularly ripe for exploitation.
The single "critical" update in the batch (MS10-087) affects Microsoft Office 2007 and 2010, which both currently contain a handy mechanism to push malware in booby-trapped emails while relying on minimal user interaction.
Andrew Storms, director of security operations at patching firm nCircle, explained: “The bug means that anyone who receives a malformed email with the preview pane enabled need only click on it to be infected with malware. The number of people using preview panes creates a giant pool of potential victims, and that makes this bug extremely attractive to hackers."
The flaw has prompted the first security patch for Microsoft Office 2010. Joshua Talbot, security intelligence manager at Symantec Security Response, added that the flaw exploits vulnerabilities in how Word handles Rich Text Format files, rather than the more common route of bobby-trapped .doc files. Malformed files can be used to execute a buffer overflow-based code injection attack on vulnerable systems.
The two remaining patches in November's litter cover lesser ("important") updates for PowerPoint and Microsoft ForeFront Unified Access Gateway (an SSL VPN product). In total the three advisories cover 11 vulnerabilities.
What is even more significant than the vulnerabilities addressed on Tuesday is an unpatched security bug in Internet Explorer. The IE zero-day, confirmed by Redmond last week, has already appeared in targeted malware attacks but a fix may have to wait until December.