Over 6 Million Chrome Extensions Found Executing Remote Commands

Security researchers have uncovered a network of over 35 Google Chrome extensions—collectively installed on more than 6 million browsers—secretly executing remote commands and potentially spying on users for years.

The alarming discovery began during a routine security review at an organization using a monitoring feature provided by Secure Annex.

Among a list of 132 extensions, several stood out because they were “unlisted”—not visible in Chrome Web Store searches and accessible only with a direct link.

While some companies use unlisted extensions for specialized deployments, this secrecy also makes it easier for malicious actors to hide their tracks.

Further investigation revealed an astonishing scope: one extension dubbed “Fire Shield Extension Protection,” with over 300,000 installations and a poor rating, masqueraded as a helpful tool but failed to deliver any meaningful functionality.

Instead, it demanded extensive permissions, ranging from access to all web traffic to managing cookies, executing scripts, and even altering browser tabs.

Suspicious URLs and Obfuscated Code

Researchers noticed multiple extensions linked to a misspelled domain, “unknow.com,” across their code—a common tactic to evade detections.

Using advanced analysis tools, the team identified 35 unique extensions sharing eerily similar background code and permission sets.

Despite varying branding and claimed purposes (ad-blocking, privacy protection, search enhancements), many of these extensions lacked real features, instead running heavily obfuscated code.

Upon installation, these extensions would appear non-functional, providing no interface or apparent purpose. However, behind the scenes, they sent regular “heartbeat” pings to external servers—specifically, URLs hosted on cloud infrastructure.

Further code analysis and AI-powered de-obfuscation revealed the ability of these extensions to receive and execute remote configuration changes, effectively giving attackers backdoor access to user browsers.

The technical capabilities of these rogue extensions were expansive:

• Harvesting all cookies from any visited domain, posing a risk to sensitive session credentials.
• Injecting and executing external scripts in active browser tabs, allowing manipulation or data theft from any site.
• Monitoring user browsing activity and sending detailed logs back to remote servers.
• Modifying browser search providers to hijack user searches and monetize traffic via ad networks.
• Accessing sensitive HTTP headers such as ‘Authorization’ and ‘Cookie’, potentially facilitating account takeovers.

Alarmingly, the extensions’ configuration—such as the level of data collection or surveillance—could be remotely updated by command-and-control servers, letting the attackers dial up their activity at any time.

Many of the extensions traced their origins back as far as 2019, and at least one, Cuponomia, was linked to a legitimate company but still exhibited aggressive tracking behaviors.

The consistent use of unlisted extensions, minimal apparent functionality, and widespread code obfuscation allowed them to evade both user suspicion and security scanners for years.

The scope of this breach—over 6 million installations—is a stark reminder of the risks lurking within browser extensions. Security experts recommend:

• Periodically reviewing installed extensions and removing any with excessive permissions or unclear origins.
• Favoring only extensions with transparent privacy policies, open-source code, and strong user ratings.
• Organizations should monitor and restrict the use of unlisted or unverified extensions in corporate environments.

Google has been notified and is conducting an internal review. Users are urged to check for suspicious extensions and report any risks immediately.

This incident underscores the importance of ongoing vigilance, as seemingly innocuous software components can quickly become vectors for far-reaching cyberattacks.

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