Microsoft Blocks ActiveX in Office Apps by Default to Boost Security and Reduce Risks

Microsoft Tightens Security by Blocking ActiveX in Office Apps by Default​

Microsoft has taken a decisive step to enhance the security of its Office suite on Windows by making it considerably harder to enable ActiveX controls. This move targets the Windows versions of popular productivity applications such as Word, Excel, PowerPoint, and Visio. Beginning this year, the default configuration blocks ActiveX content entirely, a dramatic shift from prior behavior where users were prompted to enable ActiveX controls with minimal restrictions.
This article delves deep into the background, the implications of this change, and what users and organizations should expect as Microsoft phases out ActiveX in favor of modern, safer alternatives.

The Legacy and Risks of ActiveX Controls​

ActiveX technology dates back to the mid-1990s, developed by Microsoft as part of its Component Object Model (COM) framework. Its goal was to enable embedding of interactive content — such as animations, videos, and interactive buttons — inside applications and web pages, especially Internet Explorer. ActiveX controls became a cornerstone in creating dynamic experiences across Microsoft Office documents and bespoke enterprise applications.
Despite its innovative utility, ActiveX’s deep integration with the Windows operating system came with serious vulnerabilities. These controls often ran with high privileges and minimal sandboxing, allowing attackers to exploit them:

• Malicious ActiveX controls could run unauthorized code.
• Attackers used social engineering tactics to trick users into enabling unsafe ActiveX content.
• Exploits leveraging ActiveX were common vectors for malware infections and data breaches.

Over the years, attackers continuously abused ActiveX to spread dangerous payloads, hijack systems, and pivot attacks. Security researchers consistently flagged ActiveX as a high-risk attack surface due to its permissive nature and the difficulty in fully securing legacy implementations.

The Shift in Microsoft 365 and Office Security Posture​

Reflecting evolving cyber threats and modern security expectations, Microsoft has overhauled its policy regarding ActiveX in Windows-based Office applications. Instead of prompting users with a largely permissive dialog for enabling ActiveX controls, Office apps launched from version 2504 (build 18730.20030 or newer) now block all ActiveX content by default without any user prompt.

What This Means for Users​

When a user opens an Office document containing ActiveX controls:

• A notification bar appears stating, “BLOCKED CONTENT: The ActiveX content in this file is blocked.”
• No button to enable the content is displayed.
• ActiveX controls remain disabled and, in many cases, will appear as static, non-interactive elements.

This change by default significantly reduces the risk that users inadvertently activate harmful ActiveX components that could compromise their device or network.

How to Reactivate ActiveX If Absolutely Necessary​

Microsoft recognizes that some enterprises and users still rely on legacy documents and applications built around ActiveX technology. For those cases, re-enabling ActiveX is still possible via a manual setting tweak:

1. Open the Office application (Word, Excel, etc.).
2. Go to File > Options > Trust Center.
3. Click Trust Center Settings.
4. Select ActiveX Settings.
5. Change the setting to Prompt me before enabling all controls with minimal restrictions.
6. Confirm and exit.

Still, Microsoft advises caution since re-enabling ActiveX reopens the old security risks it intends to close by default.

Why Block ActiveX?​

Microsoft’s decision stems from long-standing issues surrounding ActiveX's security vulnerabilities:

• Reduction of Malware Vectors: ActiveX has been a recurrent vehicle for malware, often tricking users into enabling dangerous controls embedded in Office files.
• Stopping Social Engineering Exploits: Many attacks relied on users consciously enabling ActiveX content when prompted. Removing the prompt entirely removes this exploitation channel.
• Alignment with Industry Security Standards: Modern cybersecurity best practices promote restricting execution of legacy code with high system access. Blocking ActiveX content fits within a broader zero-trust security model approach.
• Past Practice in Microsoft’s Security Strategy: This move follows similar actions like disabling VBA macros automatically by default in 2022 — known also as a major vector for malicious code execution within Office documents.

Ultimately, this is about tightening the attack surface and making the Office ecosystem safer for millions of users.

Impact on IT Administrators and Enterprises​

The mass deactivation of ActiveX content by default will require IT teams to adjust policies and workflows:

• Legacy Document Audits: Organizations must audit their existing document repositories for legacy ActiveX components.
• Migrations and Alternatives: Teams should start plans to migrate critical ActiveX-dependent processes to modern solutions or Office add-ins based on safer technologies.
• Security Policy Updates: IT should prepare to implement controlled exceptions only for documents that must run ActiveX controls, limiting risk exposure.
• User Education: Training users becomes paramount to recognize why ActiveX is blocked and how to proceed safely if it must be re-enabled.
• Security Posture Enhancement: Organizations should pair ActiveX blocking with robust endpoint protection, vulnerability scanning, and intranet security policies.

Though this creates some immediate challenges, the long-term result boosts defenses against email-borne threats, phishing attacks, and zero-day exploits targeting Office apps.

The Legacy Dependency Problem​

One hurdle is the reality that some business-critical applications and legacy solutions remain dependent on ActiveX. Particularly industries or companies that invested heavily in custom Office solutions have to navigate the tough balance between operational continuity and security enhancement.
For these scenarios, Microsoft offers a grace period of opt-in enabling to ensure business operations aren’t instantly disrupted. However, this is expected to be temporary as ActiveX gradually gets phased out.

Comparing ActiveX with Modern Office Add-ins​

Modern Office add-ins employ web-based technologies like HTML5, JavaScript, and REST APIs designed with security, cross-platform compatibility, and sandboxing in mind. Compared to ActiveX, modern add-ins:

• Offer better security through granular permissions and execution controls.
• Work across Windows, Mac, and web versions of Office, unlike ActiveX which is Windows-only.
• Are simpler to deploy and update via the cloud.
• Adhere to modern development standards emphasizing least privilege, auditability, and isolation.

Microsoft’s move is part of encouraging developers and organizations to adopt these modern, safer alternatives.

Platform Differences: Mac and Web Never Supported ActiveX​

It is noteworthy that Microsoft had never brought ActiveX support to the Mac or web versions of Office. This naturally positioned those platforms with better built-in security against ActiveX-based threats.
By blocking ActiveX by default on Windows Office apps, Microsoft now aligns all platforms under a more unified and secure posture.

A Look Ahead: The Final Phase-out of ActiveX?​

Microsoft’s recent update to block ActiveX content by default in the subscription-based Microsoft 365 apps strongly signals an eventual full retirement of ActiveX technology in Office. While the controls are not removed immediately, this form of gradual alienation prepares users and enterprises to adjust to an ActiveX-free future.
Future Office updates may completely remove the ability to interact with or run ActiveX controls once robust replacement add-ins and APIs are widely adopted.

Navigating the Transition: Actionable Steps and Best Practices​

For organizations and users facing this transition, several recommendations can help ease the impact:

• Audit and Catalog: Identify and document any Office files or applications relying on ActiveX.
• Testing: Validate how these documents behave with ActiveX blocked and identify any processes impacted.
• Plan Migration: Start migrating legacy features to secure add-in frameworks.
• Educate Staff: Conduct sessions to prepare end users on new Office security features and alternatives.
• Apply Controlled Exceptions Sparingly: Enable ActiveX only where absolutely necessary, with strict monitoring.
• Stay Informed: Follow Microsoft’s ongoing announcements to prepare for future deprecation timelines.

Conclusion: Advancing Office Security One Step at a Time​

Microsoft’s decision to block ActiveX by default in Office apps on Windows marks a pivotal shift in enhancing security within the widely used productivity suite. While it disrupts legacy workflows reliant on ActiveX, it effectively removes a long-exploited pathway for malware and unauthorized code execution.
The move fits a broader industry trend emphasizing zero-trust security, safer scripting frameworks, and cross-platform compatibility. As businesses and users adapt, the community gains a more secure Office experience better suited for today’s threat landscape.
Embracing modern add-ins and security best practices will lead to a safer and more efficient digital workspace. Microsoft’s evolving approach highlights that in cybersecurity – no legacy, no matter how entrenched, can outweigh safety.
Stay informed, prepare for change, and welcome an Office ecosystem that prioritizes your security above all.

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This article aims to provide a thorough, up-to-date perspective on Microsoft's evolving ActiveX policy in Office, empowering readers to understand the change's importance and navigate its implications effectively .

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Source: Neowin Microsoft makes it harder to enable ActiveX in Office apps to improve security