Researchers have identified a fresh security flaw in Microsoft's Internet Explorer Web browser and Outlook e-mail client which can leave systems open to malicious code inserted in e-mails or Web pages, network security consultancy Pivx Solutions LLC said Wednesday.
The hole is created by what is known as a cross-domain scripting flaw. In this case it means that HTML Version 4 objects embedded in Web pages and e-mails can include code that allows an attacker to access vulnerable machines, read files and documents, and execute programs on the computer, Pivx said in an advisory.
Pivx described the vulnerability as "extremely high risk" as it allows the arbitrary execution of programs, unprivileged reading of files, and stealing of server cookies.
The flaw occurs because of the Object element used to embed external objects inside an HTML 4 page. Such objects can be the WebBrowser control and other ActiveX controls, images, applets and more. The Object property of embedded WebBrowser controls is not subject to the Cross Domain security checks that embedded HTML documents ordinarily go through, and as such it is possible to escape any sandboxing and security zone restrictions, Pivx said.
In testing, Pivx has demonstrated the flaw in IE 5.5 running on Windows 98 and Windows NT and on IE 6 running on Windows 2000. The flaw also affects the Outlook and Outlook Express e-mail clients.
A quick workaround for end users involves disabling ActiveX, or setting "Script ActiveX controls marked safe for scripting" to Prompt or Disable, according to the Pivx advisory.
The flaw was discovered on June 25, and Microsoft was informed the same day, Pivx said.
Pivx decided to release its findings in the light of a survey last month by consulting firm Hurwitz Group, regarding the disclosure of security flaws.
"End users surveyed for the report are clearly angry that vendors are releasing insecure applications, and then not responding when flaws are detected," Hurwitz wrote in the report. "While it seems that putting their own companies at risk (by publicizing a flaw before a patch is available) seems counter-intuitive, end users are so frustrated with unresponsive vendors that they are willing to try almost anything."
The IDG News Service is a Network World affiliate.
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