Microsoft has released a new security patch for Internet Explorer 5.5

13 December 2001 Cumulative Patch for IE

This is a cumulative patch that, when installed, eliminates all previously discussed security vulnerabilities affecting IE 5.5 and IE 6. In addition, it eliminates three newly discovered vulnerabilities.

- The first vulnerability involves a flaw in the handling of the Content-Disposition and Content-Type header fields in an HTML. stream. These fields, the hosting URL, and the hosted file data determine how a file is handled upon download in Internet Explorer. A security vulnerability exists because, if an attacker altered the HTML header information in a certain way, it could be possible to make IE believe that an executable file was actually a different type of file -- one that it is appropriate to simply open without asking the user for confirmation. This could enable the attacker to create a web page or HTML mail that, when opened, would automatically run an executable on the user's system. This vulnerability affects IE 6.0 only. It does not affect IE 5.5.

- The second vulnerability is a newly discovered variant of the Frame Domain Verification vulnerability discussed in Microsoft Security Bulletin MS01-015. The vulnerability could enable a malicious web site operator to open two browser windows, one in the web site's domain and the other on the user's local file system, and to pass information from the latter to the former. This could enable the web site operator to read, but not change, any file on the user's local computer that could be opened in a browser window. This vulnerabilty affects both IE 5.5 and 6.0.

- The third vulnerability involves a flaw related to the display of file names in the File Download dialogue box. When a file download is initiated, a dialogue provides the name of the file. However, in some cases, it would be possible for an attacker to misrepresent the name of the file in the dialogue. This could be invoked from a web page or in an HTML email in an attempt to fool users into accepting unsafe file types from a trusted source. This vulnerabilty affects both IE 5.5 and 6.0.

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