Microsoft says customers can now disable the execution of JScript (JScript.dll) in Internet Explorer 11 after installing the October 2020 Windows monthly security updates.
JScript is an older Microsoft implementation of the ECMAScript language specification in the form of an Active Scripting engine.
Adding an option to disable JScript execution is a huge security, as it allows IT admins to provide their users with a more secure browsing experience in corporate environments where IE11 is still the web browser of choice for legacy software solutions.
“Blocking Jscript helps protect against malicious actors targeting the JScript scripting engine while maintaining user productivity as essential services continue to function as usual,” Microsoft explains.
How to disable JScript
First of all, to be able to disable JScript execution in Internet Explorer you will first need to install the IE cumulative security update released in April 2017 (or later).
Additionally, before disabling IE JScript execution on Windows 8, Windows 8.1, and Windows 10 versions 1507 to 1709, it must be enabled using an internet – instructions for configuring such a key are available here.
To manually disable IE JScript execution in Internet Explorer for Internet Zone and Restricted Sites Zone, you must follow the following procedure:
1.Click the Start, click Run, type regedt32 or regedit , and then click Ok.
2.To disable JScript execution in the Internet Zone, locate the following registry subkey in Registry Editor:
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Internet Settings\Zones\3\140D
To disable JScript execution in the Restricted Sites Zone, locate the following registry subkey in Registry Editor:
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Internet Settings\Zones\4\140D
3. Right-click the appropriate registry subkey, and then click Modify.
4.In the Edit DWORD (32-bit) Value dialog box , type 3 .
5.Click OK , and then restart Internet Explorer.
After this, Internet Explorer will no longer run JScript from websites that use features (IE9 and earlier), as well as from those in the Internet Zone or Restricted Sites Zone.
To re-enable JScript execution for one or both security zones, you must set the value of the corresponding registry subkey to 0 and restart Internet Explorer for the change to take effect.
