Security hole found in Microsoft Internet Explorer

Georgi Guninski, a well-known Bulgarian bug hunter, on Monday posted a security advisory on his Web site. Guninski ranks the problem as high risk.

Malicious Web masters can exploit so-called ".chm" files, a compressed help file format, to execute arbitrary programs on a user's computer, Guninski said. The bug also allows viewing of temporary Internet files stored on the user's hard drive.

Guninski said he reported a similar vulnerability to Microsoft "some time ago". The software was fixed by allowing .chm files to run programs only if the .chm was loaded from the local system. Guninski says this is no longer a limitation. He discovered a way Web masters could access temporary Internet files on other users' machines. Explorer saves pages in a folder called "temporary Internet files."

"It is possible to find the temporary Internet files folder," Guninski said.

Explorer creates several of these folders on a PC using random names. With a special HTML (Hypertext Markup Language) document, a malevolent Web master can reveal the name and location of a temporary Internet files folder.

Once a folder name is known it is possible to cache a .chm file in any folder and execute it, Guninski said.

Until Microsoft has issued a patch for the problem users can protect their computer by disabling active scripting, a browser function that has repeatedly been associated with security issues.

Affected programs are Microsoft's Internet Explorer versions 5 and higher. Because Explorer is integrated in Microsoft's e-mail clients Outlook and Outlook Express are also affected. Other versions may also be unsafe, but those have not been tested, Guninski said in his advisory.

Microsoft could not be immediately reached for comment.

Georgi Guninski is at http://www.guninski.com/

Join the PC World newsletter!

Error: Please check your email address.
Rocket to Success - Your 10 Tips for Smarter ERP System Selection
Keep up with the latest tech news, reviews and previews by subscribing to the Good Gear Guide newsletter.

Joris Evers

PC World
Show Comments

Most Popular Reviews

Latest Articles

Resources

PCW Evaluation Team

Matthew Stivala

HP OfficeJet 250 Mobile Printer

The HP OfficeJet 250 Mobile Printer is a great device that fits perfectly into my fast paced and mobile lifestyle. My first impression of the printer itself was how incredibly compact and sleek the device was.

Armand Abogado

HP OfficeJet 250 Mobile Printer

Wireless printing from my iPhone was also a handy feature, the whole experience was quick and seamless with no setup requirements - accessed through the default iOS printing menu options.

Azadeh Williams

HP OfficeJet Pro 8730

A smarter way to print for busy small business owners, combining speedy printing with scanning and copying, making it easier to produce high quality documents and images at a touch of a button.

Andrew Grant

HP OfficeJet Pro 8730

I've had a multifunction printer in the office going on 10 years now. It was a neat bit of kit back in the day -- print, copy, scan, fax -- when printing over WiFi felt a bit like magic. It’s seen better days though and an upgrade’s well overdue. This HP OfficeJet Pro 8730 looks like it ticks all the same boxes: print, copy, scan, and fax. (Really? Does anyone fax anything any more? I guess it's good to know the facility’s there, just in case.) Printing over WiFi is more-or- less standard these days.

Ed Dawson

HP OfficeJet Pro 8730

As a freelance writer who is always on the go, I like my technology to be both efficient and effective so I can do my job well. The HP OfficeJet Pro 8730 Inkjet Printer ticks all the boxes in terms of form factor, performance and user interface.

Michael Hargreaves

Windows 10 for Business / Dell XPS 13

I’d happily recommend this touchscreen laptop and Windows 10 as a great way to get serious work done at a desk or on the road.

Featured Content

Latest Jobs

Don’t have an account? Sign up here

Don't have an account? Sign up now

Forgot password?