Microsoft (MSFT) Windows Phone boss Joe Belfiore has added handling the company’s Internet Explorer (IE) unit to his existing duties, replacing longtime browser honcho Dean Hachamovitch, who’ll be heading a new, undisclosed team.

CNET picked up the change in Belfiore’s responsibilities from his Twitter account, where he confirmed, “everyone asking: I’m still doing phone work, just adding IE & Windows UX [user experience] as part of my next role focused on phone/tablet/pc.”

Hachamovitch, Microsoft’s previous Internet Explorer vice president, and a champion of the browser’s improvement, will be taking a new position, writing in a blog post, “I’m changing roles at Microsoft, and excited to start a new team to take on something new. Microsoft will of course continue to invest in the browser, in Web standards, in developer tooling for the Web, in privacy, and in even more areas than before. There’s a new set of capable leaders who will continue the strong work.”

Hachamovitch handled a number of IE releases, successfully recruiting development resources as Firefox and Google’s (GOOG) Chrome took hold in the market. He is a 23-year company veteran who began his career at the software giant working on Word and Office.

While IE doesn’t hold near the market position it commanded in the early days, it is kind of holding its own. In Statcounters latest share figures for October, Chrome held 40 percent of the market, followed by IE at about 29 percent, Firefox at 18 percent, Apple’s (AAPL) Safari at 8.5 percent and Opera at slightly more than 1 percent stake.

Chrome has expanded its lead on IE from a year ago when it controlled about 35 percent of the market to IE’s 32 percent and Firefox’s 22 percent. Chrome’s gains to its present 40 percent share have been made a bit more at Firefox’s expense than IE’s.

IE Security Flaw Exposed

Belfiore takes over IE just as Microsoft issued a patch for the latest IE zero-day flaw for a vulnerability discovered by security firm FireEye present in all supported versions of Windows and IE.

Writing in a blog post on Nov. 8, FireEye researchers Xiaobo Chen and Dan Caselden described the malware: “FireEye Labs has identified a new IE zero-day exploit hosted on a breached website based in the U.S. It’s a brand new IE zero-day that compromises anyone visiting a malicious website; classic drive-by download attack. The exploit leverages a new information leakage vulnerability and an IE out-of-bounds memory access vulnerability to achieve code execution.”

In the attacks, malicious code is inserted directly into a strategically important website, “known to draw visitors that are likely interested in national and international security policy,” the researchers said. The hackers are able to take control of the website and use it to attack its visitors.

FireEye said because the payload is “shellcode,” decoded and loaded into memory after following a series of steps, the attacks are difficult to track. 

“It doesn’t ever write itself to disk, a trait that leaves few to no artifacts for security defenders or forensic investigators to identify infected computers,” the company said. 

The security researcher didn’t identify the infected website.