Microsoft has announced that it is moving away from Jscript in Windows 11 24H2 to make scripting more secure, and boost Windows 11 security overall.
The change sees the company enabling JScript9Legacy by default in the latest version of Windows 11. Despite stressing the important security implications of the change, Microsoft is not changing from Jscript to JScript9Legacy in operating system edition prior to Windows 11 24H2.
Switching the default scripting engine is not something that users will have to do anything about, and for the vast majority of people there will be no noticeable change. JScript9Legacy will be automatically enabled by default and used to handle all scripting processes and operations that previously used Jscript.
Why does this matter?
Boosting Windows 11 security
Microsoft’s Naveen Shankar explains the importance of embracing JScriptLegacy, saying:
Based on JScript9, the new JScriptLegacy scripting engine offers improved performance and security features. JScript9Legacy is designed to be more compatible with modern web standards, which helps mitigate the risk of cross-site scripting (XSS) and other web-based attacks.
He goes on to say:
The new engine incorporates advanced security features such as improved handling of JavaScript objects and stricter execution policies, which make it harder for malicious scripts to exploit the system. By replacing JScript.dll with JScript9Legacy.dll, the operating system can better defend against a wider range of security threats, ultimately providing a more secure environment for users.
The change is very much about security, with Jscript being almost three decades old, and is now incredibly out of date, riddled with vulnerabilities, and simply not up to the task of meeting modern needs.
Although Microsoft says that the switch from Jscript to JScript9Legacy should be seamless, it is nonetheless prepared for the possibility that there may be compatibility issues for some users. The company is not – yet, at least – publicly sharing information about how to roll back to Jscript if there are incompatibility issues with JScript9Legacy, presumably out of concern that this is something that could be exploited by bad actors.
However, anyone that is negatively impacted by the change in scripting engine is invited to connect the support team through Services Hub for guidance on rolling back to Jscript.
It is not clear why the change only applies to Windows 11 24H2, or if there are yet-to-be-announced plans to update the scripting engine for older versions of Windows further down the line. But with Microsoft ditching Windows 10, and always eager for everyone to be running the very latest version of Windows 11, it does seem unlikely.
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