Microsoft on Tuesday sprung six patches to correct 19 vulnerabilities across its product line.
It said most pressing was two of the four "critical" patches, led by MS12-071, which addressed three previously unknown vulnerabilities in Internet Explorer 9. Internet Explorer 10 was not affected.
Likmost browser vulnerabilities of this nature, users could be infected by drive-by download.
The other critical fix of note was MS12-075, which involved three privately reported TrueType font file flaws in the Windows kernel.
"Microsoft has been dealing with font issues for a while," Paul Henry, security and forensic analyst at Lumension.
"TrueType fonts can be embedded all over the place, and Windows kernel mode driver renders the font. If these fonts are embedded in a browser or a Word document, for example, it's rendered in the kernel mode driver and winds up becoming a kernel mode exploit."
In the past, this class of vulnerability has been used to spread sophisticated malware, such as the espionage trojan Duqu.
A further two critical patches were listed including two remote-code vulnerabilities in Windows Briefcase versions XP through 7, and another that addressed five bugs in the .NET Framework.
Of the remaining bulletins, one is rated important and involved an Excel flaw, while the other was deemed moderate and corrected a single vulnerability in Internet Information Systems, which "could allow information disclosure if an attacker sends specially crafted FTP commands to the server," according to Microsoft.