Dark Reading is part of the Informa Tech Division of Informa PLC

This site is operated by a business or businesses owned by Informa PLC and all copyright resides with them.Informa PLC's registered office is 5 Howick Place, London SW1P 1WG. Registered in England and Wales. Number 8860726.

Risk

IE 8 Security Features Could Be Turned Against Users, Researchers Say

At Black Hat Europe, presenters show how filters designed to prevent cross-site scripting can be used to launch those very attacks

The good news is that Microsoft's Internet Explorer 8 browser offers a new set of filters designed to prevent some cross-site scripting (XSS) attacks. The bad news is that those same filters could be used to enable XSS attacks.

That was the gist of a presentation offered today by security researchers David Lindsay and Eduardo Vela Nava at the Black Hat Europe conference in Barcelona, Spain.

In a paper (PDF) presented at the conference, the researchers described several methods that attackers could use to enable XSS on sites that would otherwise be immune to XSS.

"There's an irony here because you're using filters that are designed to improve security to launch attacks on sites that take security seriously," said Lindsay during a telephone interview prior to the presentation.

The vulnerabilities were found in several filters that Microsoft added to IE 8 to help identify and "neuter" simple XSS attacks, Lindsay explained.

"The filters work by scanning outbound requests for potential malicious strings," the paper states. "When such a string is detected, IE 8 will dynamically generate a regular expression matching the outbound string. The browser then looks for the same pattern in responses from the server.

"If a match is made anywhere in the server's response, then the browser assumes that a reflected XSS attack is being conducted, and the browser will automatically alter the response so that the XSS attack will be unsucessful.

"The exact method used to alter a server's response is a crucial component in preventing XSS attacks. If the attack is not properly neutralized, then a malicious script may still execute. On the other hand, it is also crucial that benign requests are not accidently detected.

"The Internet Explorer 8 team decided to use a 'neutering' technique to neutralize detected attacks. More specifically, when the the filters make a positive match against the server's response, the malicious part of the response will have a certain character modified so that the attack will not execute, or not render properly."

In their presentation, Lindsay and Vela Nava demonstrated several ways in which that simple character modification strategy could be abused to allow attacks on systems that otherwise would not be vulnerable to XSS.

"The neutering mechanism can be abused by an attacker to block benign content on a page," the paper says, altering the way a page is rendered. "For example, embedded JavaScript can be blocked from executing by 'faking' an XSS attack." This approach could paradoxically be used to disable JavaScript code that would otherwise protect the site, thus allowing an attack, the researchers say.

The researchers also outlined more complex attacks that also take advantage of the neutering mechanism.

Lindsay and Vela Nava notified Microsoft of their discovery earlier this year, and Microsoft subsequently issued a patch that alleviates the immediate problem. Google and other major sites have also been notified and have implemented fixes, as well, Lindsay says.

Have a comment on this story? Please click "Discuss" below. If you'd like to contact Dark Reading's editors directly, send us a message

Tim Wilson is Editor in Chief and co-founder of Dark Reading.com, UBM Tech's online community for information security professionals. He is responsible for managing the site, assigning and editing content, and writing breaking news stories. Wilson has been recognized as one ... View Full Bio

Comment  | 
Print  | 
More Insights
Comments
Newest First  |  Oldest First  |  Threaded View
7 Truths About BEC Scams
Ericka Chickowski, Contributing Writer,  6/13/2019
DNS Firewalls Could Prevent Billions in Losses to Cybercrime
Curtis Franklin Jr., Senior Editor at Dark Reading,  6/13/2019
Cognitive Bias Can Hamper Security Decisions
Kelly Sheridan, Staff Editor, Dark Reading,  6/10/2019
Register for Dark Reading Newsletters
White Papers
Video
Cartoon
Current Issue
Building and Managing an IT Security Operations Program
As cyber threats grow, many organizations are building security operations centers (SOCs) to improve their defenses. In this Tech Digest you will learn tips on how to get the most out of a SOC in your organization - and what to do if you can't afford to build one.
Flash Poll
The State of IT Operations and Cybersecurity Operations
The State of IT Operations and Cybersecurity Operations
Your enterprise's cyber risk may depend upon the relationship between the IT team and the security team. Heres some insight on what's working and what isn't in the data center.
Twitter Feed
Dark Reading - Bug Report
Bug Report
Enterprise Vulnerabilities
From DHS/US-CERT's National Vulnerability Database
CVE-2019-12855
PUBLISHED: 2019-06-16
In words.protocols.jabber.xmlstream in Twisted through 19.2.1, XMPP support did not verify certificates when used with TLS, allowing an attacker to MITM connections.
CVE-2013-7472
PUBLISHED: 2019-06-15
The "Count per Day" plugin before 3.2.6 for WordPress allows XSS via the wp-admin/?page=cpd_metaboxes daytoshow parameter.
CVE-2019-12839
PUBLISHED: 2019-06-15
In OrangeHRM 4.3.1 and before, there is an input validation error within admin/listMailConfiguration (txtSendmailPath parameter) that allows authenticated attackers to achieve arbitrary command execution.
CVE-2019-12840
PUBLISHED: 2019-06-15
In Webmin through 1.910, any user authorized to the "Package Updates" module can execute arbitrary commands with root privileges via the data parameter to update.cgi.
CVE-2019-12835
PUBLISHED: 2019-06-15
formats/xml.cpp in Leanify 0.4.3 allows for a controlled out-of-bounds write in xml_memory_writer::write via characters that require escaping.