Browser extensions are software modules that can be added to web browsers to enhance their functionality. They can provide a wide range of features, such as ad-blocking, password management, and improved user interface customization.
However, not all extensions are benign; some are designed with malicious intent. Malicious browser extensions can steal sensitive data, track user behavior, inject unwanted advertisements, or even take over a user’s browser entirely. In this blog, we’ll take a deep dive into what malicious browser extensions can do and how to mitigate the risks they pose.
The Risks of Malicious Browser Extensions
The introduction of malicious browser extensions into an organization’s environment can pose significant risks, notably:
- Data Theft – Malicious extensions can access and exfiltrate sensitive information such as login credentials, financial information, and personal data. In an organization, this can lead to the exposure of confidential business information, intellectual property, and client data.
- Credential Harvesting – Some malicious extensions are designed to capture usernames and passwords as they are entered on websites. This can lead to unauthorized access to corporate systems, email accounts, and other critical resources.
- Corporate Espionage – Extensions with keylogging capabilities can record every keystroke made by an employee, capturing sensitive information including emails, chat messages, and documents. This data can be used for industrial espionage, giving competitors access to trade secrets and strategic plans.
- System Compromise – Malicious extensions can serve as a vector for deploying malware, including ransomware, spyware, and remote access trojans (RATs). Once installed, these can lead to a complete compromise of the organization’s IT infrastructure.
- Data Manipulation – Extensions can modify the content of web pages, potentially leading to data tampering. For example, they could alter financial information, manipulate reports, or interfere with online transactions.
- Network Exploitation – Some extensions can exploit network vulnerabilities to spread malware across an organization’s network. They might use compromised systems to launch further attacks, escalate privileges, or create backdoors for future access.
- User Tracking and Profiling – Extensions with tracking capabilities can monitor an employee’s browsing habits, search history, and online activities. This data can be used for targeted phishing attacks or to build detailed profiles of individuals within the organization.
Malicious Browser Extensions: Real-World Case Studies
- Cyberhaven Incident – The most recent (December 2024) and most sophisticated example of an attack involving malicious extension is the “Cyberhaven Incident” caused by a phishing attack on one of its employees. The targeted phishing message was built to look exactly like a legitimate message, luring the user to click the link and login using his Google user, allowing the adversary to take control and replace Cyberhaven’ s extension, with a seemingly similar extension, however, the new uploaded extension included malicious code. This extension was automatically distributed to close to 400,000 users who are receiving automatic updates of Cyberhaven extension. This event is still under investigation, and it seems like there are at least a few more extensions were impacted with the same malicious code. The number of users impacted is estimated at over 1 million. According to reports, the malicious extensions intercepted sensitive data, including 2FA tokens, enabling unauthorized access to corporate systems.
- The Great Suspender – Originally, The Great Suspender was a popular Chrome extension used to suspend unused tabs to free up system resources. However, in early 2021, the extension was sold to an unknown entity that introduced malicious code. This code included tracking scripts and remote code execution capabilities, posing a significant threat to users’ privacy and security. Google eventually removed the extension from the Chrome Web Store.
- DataSpii Incident – In 2019, security researcher Sam Jadali uncovered a massive data leak caused by browser extensions such as Hover Zoom, SpeakIt!, and FairShare Unlock. These extensions collected and exposed sensitive information from users’ browsing sessions, including corporate data, medical records, and personal financial information. The incident highlighted the risks associated with seemingly harmless extensions and their potential to cause widespread data breaches.
- Nano Adblocker and Nano Defender – Nano Adblocker and Nano Defender were popular ad-blocking extensions that were sold to an undisclosed buyer in late 2020. Shortly after the sale, users noticed that the extensions started collecting user data and injecting malicious scripts. The extensions were eventually removed from the Chrome Web Store, but not before they had compromised the privacy and security of numerous users.
- Data Breach via Chrome Extension – In 2018, a Chrome extension designed to help users create custom keyboard shortcuts was found to be secretly harvesting users’ browsing history and sending it to a remote server. The extension, which had over 1.4 million users, was quickly removed from the Chrome Web Store, but the incident served as a reminder of the potential dangers posed by even the most innocuous-seeming extensions.
- The Fake AdBlock Plus – In 2017, a fake version of the popular AdBlock Plus extension appeared in the Chrome Web Store. This malicious clone managed to deceive over 37,000 users before it was detected and removed. The fake extension injected unwanted ads into users’ browsers, profiting from ad revenue while compromising the user experience.
Mitigating the Risks of Malicious Browser Extensions
To protect against the risks posed by malicious browser extensions, organizations should implement several key security measures, including:
- Extension Management Policies – Organizations should establish and enforce policies regarding the installation and use of browser extensions. This can include maintaining a whitelist of approved extensions and blocking all others.
- Regular Audits – Regular audits of installed browser extensions across the organization can help identify and remove any that are unauthorized or potentially malicious. IT departments should stay informed about the latest threats and update their policies accordingly.
- Employee Education – Educating employees about the risks associated with browser extensions and providing guidelines on safe practices can help reduce the likelihood of malicious extensions being installed. This includes advising against installing extensions from untrusted sources and encouraging prompt reporting of any suspicious behavior.
- Browser Security Solutions – Deploying robust browser security solutions can help detect and block malicious activities associated with browser extensions. These solutions can provide real-time risk scoring, monitoring and alerting, helping to mitigate threats before they cause significant damage.
- Access Controls – Implementing strict access controls can limit the potential damage caused by malicious extensions. This includes using least privilege principles to restrict access to sensitive data and systems.
The Bottom Line
Malicious browser extensions pose a significant threat to organizational security, with the potential to cause data breaches, credential theft, system compromise, and other serious issues. By understanding the risks and implementing appropriate security measures, organizations can protect themselves against these threats and maintain a secure browsing environment for their employees. Real-life examples such as The Great Suspender, DataSpii, and Nano Adblocker incidents highlight the importance of vigilance and proactive security practices in mitigating the risks associated with browser extensions.
For more information about Seraphic, read our Enterprise Browser Security White Paper or request a demo.
