Software Engineering Institute

The Adobe Flash Player is a player for the Flash media format and enables frame-based animations and multimedia to be viewed within a web browser. ActionScript is a scripting language that is used to develop software and multimedia files that are processed by the Adobe Flash Player. The asfunction protocol enables HTTP hyperlinks in Flash files to launch a ActionScript functions.

Per Adobe Security Bulletin APSB07-20:
This update restricts the unsupported asfunction: protocol to address potential cross-site scripting issues with some SWF files. This issue is specific to Flash Player 8 and Flash Player 9 and does not affect Flash Player 7.

Note that vulnerable versions of the Flash Player may be distributed with various operating systems.

A remote, unauthenticated attacker may be able to launch cross-site scripting attacks against sites that host vulnerable Flash files.

Update Flash Player
Adobe has released an update to address this issue. Adobe Security Bulletin APSB07-20 contains more information about obtaining fixed software. Adobe Dreamweaver users may need to manually update their Flash player to obtain updates. See the Protocol Solutions Network Security Blog Adobe/Macromedia/Dreamweaver vulnerability posting for more information.

Limit access to Flash files

Limiting access to untrusted Flash files can prevent cross-site scripting attacks that use Flash files. Disable ActiveX controls in the Internet Zone in Microsoft Internet Explorer. See Securing Your Web Browser for more information. Consider using the NoScript extension to whitelist web sites that can run Flash in Mozilla browsers such as Firefox. See the NoScript FAQ for more information.