What makes malicious Chrome extensions hard to detect?

The Chrome Web Store is widely regarded as a trustworthy source, leading users to perceive extensions from the platform as legitimate and thoroughly vetted, but this isn't always the case. Despite evidence indicating that problematic extensions can slip through review processes, the perception persists among individuals. For example, a study from the International Journal of Information Security web integrity discusses how Google concluded that about 10% of the extensions analyzed appeared harmful, usually by hiding their true purpose or making changes after they were installed.

Many harmful extensions operate by offering users the promised benefits, like ad-blocking capabilities or tools aimed at enhancing productivity. It differs from simpler forms of malware that cause direct harm to systems. Identifying risky behaviors becomes notably challenging when these behaviors are spread out across different areas of the extension system.

Extensions modify a webpage's content discreetly, connect with external servers to extract data, and depend on user actions like clicking prompts. The process involves the use of browser permissions, including options like activeTab and storage. The distributed architecture enables the monitoring of highly sensitive and hazardous sites, including email, by circumventing static analysis.

Malicious extensions often look and behave like real tools

Malicious Chrome extensions often do exactly what they promise, which is part of what makes them difficult to spot. A recent Paubox report describes 30 copycat extensions that posed as AI assistants, including fake ChatGPT- and Gemini-branded tools, and together drew more than 260,000 downloads. Users saw a convincing AI chat experience, but behind the scenes, the extensions loaded a full-screen iframe tied to an attacker-controlled domain that intercepted prompts and captured whatever people pasted into the tool, including email content, browser content, API keys, and tokens.

The type of attack can often go unnoticed, as the product appears to function normally. Users might receive a convincing summary, a revised draft, or a response from a chatbot, leading them to believe that the extension is genuine. The report notes that the malicious logic operated within a remote web application instead of the local code of the extension.

Individuals often seek out clear indicators of potential issues, including system crashes, intrusive pop-ups, or behavior that raises suspicion. Extensions that operate similarly to standard applications bypass those indicators. The apparent value they present often masks the underlying issues, making it increasingly difficult to distinguish between a genuine utility and a potentially harmful one without a thorough technical examination.

The most harmful logic may live outside the extension package

A Scientific Reports study notes, “To address the growing threat of malicious URLs, numerous ML-based techniques have been proposed by researchers. However, these approaches often face limitations due to inherent challenges. By the time a malicious URL is identified and incorporated into a blacklist, it is often too late, as many users may have already been compromised.”

The negative elements associated with an extension typically originate from remote servers under the control of the attacker. The code undergoes verification upon submission, which can obscure potential dangers, complicating the identification of threats. Meanwhile, the primary developments are taking place in a different location.

An extension may request various permissions, such as access to tabs, the ability to make web requests, or insight into numerous aspects of the user's browsing activities. Once installed, it can leverage that access to obtain information or instructions from external servers. The installation of the extension may lead to a change in the undesirable behavior, while the extension itself remains unchanged.

Remote logic can enable a malicious extension to compromise sensitive data such as cookies and passwords, alter webpage content, introduce misleading prompts, or disrupt active sessions. Certain functions are activated only under specific conditions, such as when a user visits a particular website or performs a designated action. Certain individuals have the ability to disguise their traffic as ordinary background communication, complicating the task of distinguishing between suspicious behavior and routine activity.

Permissions can be broad, but users rarely understand them

According to the previously referenced International Journal of Information Security study, “The key problem with extensions is that, once installed, they possess over-privileged capabilities that may be abused by attackers.”

Some permissions let an extension run on a lot of websites, change what shows up on the page, or work with browser traffic in the background. That can make a lot more people see it than the average user thinks, especially if the extension seems safe and does something valuable.

The bigger problem is that permissions only disclose what an extension can do. A respectable productivity tool and a bad extension may seek the same kinds of access. The request may look the same on the surface. Real risk only becomes obvious after installation when the access is misused. It is why it can be hard to notice harmful conduct early on.

Why Paubox is a solution

Paubox is the right answer when the true problem is encryption and getting users to always use secure email correctly. In a lot of healthcare environments, personnel work quickly, use regular inbox processes, and make mistakes when security depends on steps that have to be done by hand.

It works with Google Workspace and Microsoft 365, automatically encrypts outgoing emails, and enables recipients read messages in their regular inbox instead of having to go through portals or enter extra credentials.

Users are less likely to use a system if it has additional stages. Paubox also signs a business associate agreement, which is a standard need when a vendor handles protected health information. Its higher-tier plans incorporate security against spam, malware, and phishing. In reality, the value is clear: it strives to make the safe choice the default choice.

See also: HIPAA Compliant Email: The Definitive Guide (2026 Update)

FAQs

What is malware in a browser extension?

Malware in a browser extension is harmful code hidden inside a tool that appears useful or legitimate.

What kind of data can a malicious extension steal?

A malicious extension may collect login details, cookies, email content, browser activity, saved form entries, API keys, tokens, and other sensitive information pasted into web pages or extension interfaces.

Why are malicious extensions hard to detect?

Malicious extensions often avoid obvious warning signs. They may not crash the browser or show intrusive pop-ups.