From Convenience to Catastrophe: The Real Cost of Unchecked Browser Extensions

Why Browser Extensions Are a Growing Security Threat

Browser extensions have become a staple in the browsers of most end-users. Extensions allow browsers to have extended capabilities, features, and integrations that make them even more useful. However, with the added benefits come a wealth of security risks. . In the past year alone, multiple high-profile breaches have demonstrated how malicious or compromised extensions can lead to data leaks, unauthorized access, and financial losses for businesses.

In this article, we’ll explore recent browser extension security incidents, their impact, and how businesses can protect themselves.

The Rise of Browser Extension Threats

With over 180,000 extensions available on the Chrome Web Store, browser extensions are now as common as the browsers they integrate with. However, this widespread adoption has also increased security risks.

According to Spin.AI’s 2024 report of browser extension risks:

• 48% of browser extensions request excessive permissions – Many browser extensions request more than the appropriate set of permissions from the end-user to carry out the functionality they were intended to carry out. This can lead to them having permissions to read browsing history, intercept network traffic, and modify webpage content.
• 35% of browser extensions are high-risk – High-risk extensions are those that pose threats such as credential theft, session hijacking, and data exfiltration
• Over 400 million users have downloaded at least one compromised extension in the past two years

5 Notable Browser Extension Security Breaches

Let’s look at five recent browser extension compromise attacks where unchecked browser extensions led to security incidents and data breaches.

1. Cyberhaven Chrome Extension Breach

What Happened: At the end of last year, December 2024, Cyberhaven, a data protection company, suffered a security breach. Evidently, with a successful phishing campaign, attackers were able to steal developer’s credentials allowing them to publish a malicious update to Cyberhaven’s own browser extension.

Impact:

• Users with the Cyberhaven extension installed were at risk of their session tokens and cookies being stolen, which would allow attackers to hijack accounts.
• The compromised extension (version 24.10.4) was available for approximately 25 hours, from December 24, 2024, at 8:32 PM ET to December 25, 2024, at 9:50 PM ET
• A total of around 35 Chrome extensions were compromised
• The breach lasted several hours before detection, and affected 3.7 million users

How Browser Extensions Contributed to the Breach: Attackers were able to exploit the automatic update mechanism of browser extensions. When they published the malicious version, all users automatically received the compromised update and were at risk of exposure.

2. Capital One Shopping Browser Extension Lawsuit

What Happened: In January 2025, influencers Jesika Brodiski and Peter Hayward filed a class-action lawsuit against Capital One. They alleged that its Shopping browser extension manipulated affiliate links to steal commission earnings from content creators and pocket the commission.

Impact:

• The extension is used by approximately 10 million users
• Influencers lost thousands of dollars in legitimate affiliate commissions
• The lawsuit highlights unethical practices and potential financial losses for those with affiliate marketing UTM codes

How Browser Extensions Contributed to the Breach: The Capital One Shopping extension has scripts injected into users’ browsers that replace the original affiliate tracking codes and making sure that Capital One benefited from the affiliate sale instead of the original referrer. 

This particular breach shows the power of malicious or unscrupulous browser extensions to steal and manipulate data mid-stream.

3. LastPass data breach

What Happened: In late 2022, LastPass, which is a well-known password manager, suffered a serious data breach. Attackers were able to gain access to user data, billing information, and encrypted password vaults. While some of the data was still encrypted, other subsets of data were not. This led to a potential exposure of sensitive information. 

Impact:

• Users’ encrypted password vaults were compromised. This required customers to initiate immediate password changes across the board
• The breach led to a loss of trust in LastPass and other cloud-stored password managers

How Browser Extensions Contributed to the Breach: The LastPass browser extension which provides the core of the LastPass password management functionality immediately became an attack vector for the breach. Attackers exploited vulnerabilities to access sensitive user data. This highlights the risks associated with browser extensions and that become compromised or coexist with another browser extension that is compromised.

4. Avast and AVG Browser Extensions Data Collection Scandal

What Happened: In late 2019, there were browser extensions developed by Avast and its subsidiary company, AVG, that were collecting detailed user browsing data without consent from the user. The companies were then selling the data to third parties for marketing and analytics purposes. 

Impact:

• The data collection from the extensions developed by Avast led to the extensions being removed from most of the major browser extension stores, including Google Chrome and Mozilla Firefox.
• This was damaging to user’s confidence in the company as their sensitive data was compromised and exposed to third-parties without consent
• The FTC banned Avast from selling browsing data for advertising and required it to pay $16.5 million

How Browser Extensions Contributed to the Breach: The extensions were marketed as security tools. Under that role, they had permissions that allowed them to monitor and snoop on user activity. This capability was exploited to gather extensive browsing information and then monetized at the expense of user’s private information

5. Honey Browser Extension Allegations

What Happened: In December 2024, PayPal’s Honey Browser extension, was part of a controversy as it was accused of misleading users by giving precedence to certain business partners’ discount codes over better deals.

Impact:

• Unsuspectingly, users may have paid higher prices by not getting the best discount they would have otherwise received had they not been using the honey browser extension.
• Influencers and businesses who use affiliate codes saw commission losses as a result of the unfair practices related to the extension

How Browser Extensions Contributed to the Breach: Honey browser used its permissions to analyze user purchases and give priority to deals that benefited its own business interests over better savings for users.

How to Protect Against Malicious Browser Extensions

As shown, browser extensions can lead to data leaks, compromised session tokens and passwords, unscrupulous business practices, and lost revenue. As users, including in the enterprise, are using more browser extensions than ever before, how can businesses protect themselves?

1. Audit Extension Permissions

• Review the permissions requested by browser extensions before installing them
• Don’t use extensions that request excessive permissions, like access to all websites and network activity
• Look at the history of the plugin. Who develops it? What is their reputation?
• What do the reviews look like?

2. Monitor Installed Extensions

• Individuals need to inventory and monitor the browser extensions installed and make sure these don’t change or request new types of permissions
• Companies need to monitor and control the use of extensions. This includes detecting and blocking high-risk add-ons.

3. Conduct Regular Extension Audits

• Organizations should carry out frequent audits of their browser extensions, continuously if possible
• IT teams should enforce extension allow lists, allowing only extensions that are approved by the business

4. Watch for Suspicious Activity

• Watch for unexpected browser behaviors, redirects, or slow downs. Keep an eye on increased data usage, or unauthorized access attempts.
• Use endpoint security solutions that can detect browser threats

5. Train Employees on Cybersecurity Best Practices

• Employees need to be trained on how to identify and report suspicious browser extensions
• Make sure to train users to read reviews and check extension release history and reviews before installing new extensions

How Spin.AI Protects Against Browser Extension Threats

The Spin.AI solution offers a comprehensive way to protect against browser-based threats and dangerous third-party SaaS applications. It helps to protect against the types of extension threats we have seen in the breaches listed above. How could Spin.AI have mitigated these recent incidents?

• Complete assessment – Spin.AI uses multiple risk signals to help determine if browser extensions and SaaS apps are risky. These include a combination of both technical and non-technical indicators.The technical risks may include things like code vulnerabilities. Non-technical risks may include things like alignment with compliance standards and the extension’s reputation in the community.Combining the two helps to give organizations a holistic view of the overall risk profile of a particular browser extension or SaaS app.
• Continuous real-time monitoring – Spin.AI continuously monitors extensions to detect risky behaviors or when behaviors change. Any detected change, no matter how sudden, will be picked up and reflected in Spin.AI’s risk score and users will be notified of the change. Performing this type of in-depth risk analysis of each browser extension or SaaS app would not be possible using manual human effort. Spin.AI automates this process and performs the heavy lifting for organizations to enhance their security posture.
• Automated threat response – One of the powerful features of Spin.AI is the ability it gives administrators to create security policies that can immediately respond to extensions users attempt to install, or extensions already used and that become malicious to prevent users from using them. If an extension becomes compromised, the behavior will be immediately detected and Spin.AI policies will protect business-critical data from being impacted.

Final Thoughts: Secure Your Data Before It’s Too Late

Unchecked browser extensions pose serious security risks for businesses and individuals alike. Incidents like the Cyberhaven breach, Capital One lawsuit, and Avast data scandal highlight the need for stronger security policies.

By auditing permissions, monitoring extensions, and using advanced security solutions like Spin.AI, organizations can mitigate risks and protect sensitive data.Assess and manage risk in a minute, not weeks, to ensure secure enterprise browsing: Try the Free Risk Assessment Tool