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Growing Concerns Over Browser Security
The ever-growing ecosystem of browser extensions has long been a double-edged sword. While these add-ons enhance user experience by providing handy tools like color pickers, VPNs, and volume boosters, they can also serve as gateways for cyberattacks. A recent investigation by Koi Security reveals an alarming truth — nearly a dozen malicious Chrome extensions, downloaded over 1.7 million times, have been secretly spying on users and potentially redirecting them to dangerous websites. Even more troubling, some of these malicious add-ons were also discovered in Microsoft Edge’s extension store, affecting another 600,000 users. This large-scale browser hijacking operation is not only deceptive but deeply concerning, especially as many of the extensions remain available and are verified by Google, misleading unsuspecting users.
Malicious Chrome Extensions Target Millions
Researchers at Koi Security have uncovered a stealthy and large-scale malware campaign involving at least 11 Chrome extensions that appear legitimate but contain hidden, dangerous code. These extensions — including names like “Color Picker,” “Emoji Keyboard,” “Volume Max,” and “Unlock TikTok” — offer useful features but quietly track browsing behavior. Embedded within their service workers is malicious code that triggers each time a user visits a new webpage. This code captures the URL along with a unique tracking ID, which is sent to a remote server. The server can then respond with redirect instructions, hijacking user sessions and sending them to unsafe destinations.
Notably, these extensions have passed Chrome Web Store’s verification checks and amassed hundreds of positive reviews, which helps them maintain a trustworthy appearance. Some were once legitimate and only became dangerous through silent background updates delivered by Chrome’s auto-update system. This tactic allows developers — or malicious actors who hijack the developer’s account — to insert malicious functionality without user knowledge. Alarmingly, Koi Security notes that the redirection functionality, while coded in, wasn’t actively used during their analysis. However, the presence of such functionality still poses a major threat to users.
Among the flagged extensions are:
Color Picker, Eyedropper — Geco colorpick
Emoji keyboard online — copy&paste your emoji
Free Weather Forecast
Video Speed Controller — Video manager
Unlock Discord — VPN Proxy
Dark Theme — Dark Reader for Chrome
Volume Max — Ultimate Sound Booster
Unblock TikTok & YouTube
Weather
One of the most controversial extensions, “Volume Max — Ultimate Sound Booster,” had already been under scrutiny by researchers from LayerX. Though they flagged it as suspicious last month, no malicious behavior could be confirmed at the time. Now, the presence of exfiltration and redirection code confirms that the threat is real.
Koi Security also discovered similar threats in Microsoft Edge’s extension store. In total, 18 malicious browser extensions have infected over 2.3 million users. The researchers stress that users should immediately uninstall the listed extensions, clear browser data, check for malware, and monitor their accounts for any signs of intrusion.
What Undercode Say:
How Browser Extensions Became Trojan Horses
Browser extensions, once seen as innocent enhancements, are now often weaponized. The latest revelations from Koi Security underscore a dark shift in cyberattack vectors — not from zero-day vulnerabilities or sophisticated malware, but from trusted tools users willingly install. The success of this malware campaign shows how trust in platform verification systems, like Chrome’s “Verified” badges and high-rated reviews, can be easily exploited. When even featured extensions can be hijacked silently via updates, user safety becomes an illusion.
Silent Code Injection via Auto-Update
One of the most insidious aspects of this campaign is the use of Chrome’s automatic extension updates. While auto-updates are designed for user convenience and security, they also open a dangerous loophole. Developers — or attackers who have compromised them — can push updates with malicious code that users unknowingly accept. Since the malicious behavior wasn’t present in earlier versions, these updates bypass most user scrutiny, making detection extremely difficult.
Impact on User Trust and Google’s Oversight
This scandal casts doubt on Google’s ability to maintain the integrity of its Web Store. Verified badges, prominent placements, and high ratings offer a false sense of security. For users, the lesson is clear: trust must be earned through transparent behavior, not polished UI and positive reviews. It also raises the question of whether extension developers should be subject to ongoing auditing — especially when updates can dramatically change how the software behaves.
Shared Threat Landscape: Microsoft Edge Also Infected
What amplifies the concern is that similar threats exist on Microsoft Edge’s extension store. Cybercriminals understand the cross-platform nature of modern users and target both Chrome and Edge to maximize infection rates. With over 600,000 downloads recorded on Edge, it’s evident that this isn’t a one-off incident but part of a coordinated attack strategy across ecosystems.
Security Fatigue vs. Threat Awareness
Despite growing awareness, many users continue to underestimate the risks posed by browser extensions. The average user assumes anything from a major store is safe. This misplaced trust is exactly what attackers exploit. When even security researchers take time to detect hidden background scripts, how can average users stand a chance? The need for transparency and manual approval of extension updates is becoming increasingly critical.
The Rise of Hybrid Threats
These malicious extensions
🔍 Fact Checker Results:
✅ Confirmed: At least 11 Chrome extensions have been flagged for malicious behavior
✅ Verified: Over 2.3 million users affected across Chrome and Edge
❌ Not Confirmed: No active redirection attacks were observed during testing
📊 Prediction:
Given the success and scale of this campaign,
References:
Reported By: www.bleepingcomputer.com
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