Software Engineering Institute

Apple Safari is a web browser that is available for OS X and Microsoft Windows platforms. Apple Safari for Microsoft Windows will modify its behavior based on the Internet Explorer security zone settings. One of the Internet Explorer zone settings that Safari queries is URLACTION_SHELL_EXECUTE_HIGHRISK, which is stored as registry value 1806 in the Internet Explorer URL Security Zone section of the Windows registry. If this value is set to "allowed" for the associated URL Security Zone, Safari will automatically execute files, which are also automatically downloaded from the website.

For the Trusted Sites and Local Intranet zones on Internet Explorer 6 systems, this value defaults to 0x00, which indicates that the action is "allowed." This URL Security Zone setting appears to have no representation in the GUI for configuring the zones on Internet Explorer 6 systems. This means that no matter how the Trusted Sites or Local Intranet zones are configured using the graphical interface for Internet Explorer, Safari will automatically execute files that are downloaded from sites that reside in these zones.

Internet Explorer 7 systems expose the URLACTION_SHELL_EXECUTE_HIGHRISK URL Security Zone setting as "Launching applications and unsafe files" in the Internet Explorer zone security configuration dialog. This value defaults to 0x01 for the Trusted Sites zone, and 0x00 for the Local Intranet zone, which correlate to "prompt" and "allow," respectively. This means that by default, any site in the Local Intranet zone on Internet Explorer 7 systems can cause Safari to automatically execute downloaded files. Safari will automatically execute downloaded files in other zones if the "Launching applications and unsafe files" option is set to "allow."

By convincing a user to visit a specially crafted web page with Apple Safari on Windows, an attacker may be able to execute arbitrary code on a vulnerable system.

Apply an update
This issue is addressed in Safari for Windows 3.1.2. Please see the Apple Security Update for more details. This version of Safari will prompt the user before downloading or executing files.