Security Update for CAPICOM (KB931906) 2.1

Security Update for CAPICOM (KB931906) is a Microsoft-issued patch that fixes a critical vulnerability in CAPICOM, a legacy ActiveX/COM component that exposes Windows cryptographic functions for signing, encryption, hashing, and certificate management. Without this update, a specially crafted web page or file could exploit the vulnerable control and potentially execute code on the affected system.

This update replaces the vulnerable CAPICOM component with a secure version and hardens how the control can be invoked, reducing attack surface in Internet Explorer and scriptable environments. It does not add new features; it strictly addresses security and stability.

Who should install it:

• Any system with CAPICOM installed, especially those running older Windows versions (e.g., Windows XP/Server 2003) or legacy applications and scripts that rely on CAPICOM.

Additional notes:

• A restart may be required.
• Distributed via Windows Update/WSUS and as a standalone package.
• CAPICOM is deprecated; for new development, use modern cryptography APIs (e.g., .NET System.Security.Cryptography or CNG).

Security Update for CAPICOM (KB931906) is developed by Microsoft. The most popular version of this product among our users is 2.1. The names of program executable files are zlclient.exe, Updatstb.exe, updater.exe, update1.exe and update.exe.

You can check Cumulative Update for Microsoft Visual Basic, Security Update for Windows XP (KB2753842-v2), Autodesk Autodesk AutoCAD Map 3D SP2 and other related programs like Security Update for Windows XP (KB2727528) at the "download" section.