Microsoft has made a significant shift in its scripting technology for Windows 11, version 24H2 and beyond, replacing the long-standing default engine, JScript, with the more advanced and secure JScript9Legacy. This change is primarily motivated by the need to enhance security measures against a variety of web threats, including the ever-persistent cross-site scripting (XSS) vulnerabilities.
Transition to JScript9Legacy
In a statement, Naveen Shankar from Microsoft highlighted that “to provide a more secure experience, beginning with Windows 11, version 24H2, JScript9Legacy is enabled by default to handle all scripting processes and operations that previously used JScript.” This transition marks a pivotal moment for the company as it seeks to bolster the security framework of its operating system.
JScript, which debuted in 1996, has served as Microsoft’s implementation of ECMAScript, akin to JavaScript. It was widely utilized in Internet Explorer and as a scripting language for Windows, facilitating tasks such as automation, form validation, and the creation of administrative scripts. However, its relevance has diminished over the years, as it has become increasingly non-compliant with modern JavaScript security standards. The engine has been a frequent target for vulnerabilities, including memory corruption and arbitrary code execution, often exploited through malicious documents, emails, and websites.
Despite its outdated status, JScript remained the default engine on Windows for compatibility reasons, ensuring that critical systems could continue to function without disruption. However, with the deprecation of Internet Explorer and the growing adoption of the Edge browser, Microsoft has decided to take a decisive step forward by replacing JScript with JScript9Legacy.
JScript9Legacy represents a modernized iteration of JScript9, designed not only to meet legacy scripting requirements but also to enhance security and compatibility. This new engine can be utilized outside of the browser environment, offering a more robust solution for developers and users alike.
Importantly, users will not need to take any action for this transition; the switch to JScript9Legacy will occur automatically with the latest version of Windows. Existing scripts are expected to function seamlessly, preserving user workflows. In the event that compatibility issues do arise, Microsoft has assured users that a rollback to the previous engine is feasible through their support team.
