Critical Chrome Extension Vulnerabilities Let Attackers Easily Compromise Browsers

Severity

Medium

Security researchers have identified two critical vulnerabilities, dubbed MaXSS and Spyder, affecting the AI-powered browser extensions MaxAI and SiderAI. Together, these extensions have been installed more than 10 million times across Google Chrome and other Chromium-based browsers. Both extensions belong to a growing class of AI-powered browser tools that provide features such as webpage summarization, contextual assistance, content generation, and automated browsing actions. Due to their extensive browser permissions and deep integration with web sessions, these extensions possess access to sensitive user information and browser functionality. Researchers discovered that weaknesses in the extensions’ communication mechanisms could allow attackers to abuse their privileged access, potentially exposing emails, documents, authentication tokens, AI conversations, and other sensitive data.

How?

The vulnerabilities stem from improper validation of messages exchanged between websites, extension content scripts, and privileged background processes.

MaXSS (MaxAI)

The MaXSS vulnerability allows a malicious website to send specially crafted messages to MaxAI’s content script. Because these messages are insufficiently validated before being forwarded to the extension’s background process, attackers can abuse privileged browser capabilities.

Researchers demonstrated that attackers could:

Open hidden browser tabs.
Capture screenshots of sensitive applications such as Gmail and Google Calendar.
Interact with AI platforms such as ChatGPT and Claude on behalf of the user.
Extract and access sensitive information without the user’s knowledge.

Spyder (SiderAI)

The Spyder vulnerability enables malicious websites to simulate user interactions within the extension’s embedded web environments. By generating artificial events, attackers can manipulate the extension into performing actions as if they were initiated by the user.

Proof-of-concept demonstrations showed that attackers could:

Automatically enter prompts into AI applications.
Trigger button clicks and other actions.
Access AI-generated content associated with a victim’s account.
Exfiltrate sensitive information through attacker-controlled links.

Notably, exploitation of both vulnerabilities requires only that a victim visit a malicious webpage, with no additional user interaction necessary.

Recommendation

Organizations and individual users should immediately review their installed browser extensions and remove MaxAI and SiderAI if they are present, at least until security patches or official mitigations become available. Given the extensive permissions often granted to AI-powered browser extensions, users should also minimize reliance on third-party extensions, especially those that request broad access to browsing activity, website content, or browser functionality.

For enterprise environments, organizations should implement strict browser extension governance by enforcing approved-extension policies and maintaining allowlists of trusted extensions. Limiting the installation of unauthorized extensions can significantly reduce the attack surface and prevent potentially vulnerable or malicious tools from gaining access to sensitive corporate data.

Security teams should continuously monitor browser activity for indicators of suspicious behavior, including unauthorized tab creation, automated interactions, unexpected screenshots, or unusual communication between websites and browser extensions. Regular audits of extension permissions should also be conducted to identify and remove unnecessary access rights that could be abused by attackers.

In addition, organizations should educate users about the security risks associated with AI-powered browser extensions and the potential impact of browser-based attacks. Deploying endpoint detection and monitoring solutions capable of identifying anomalous browser and extension activity can provide an additional layer of defense. Finally, maintaining up-to-date browsers, extensions, and security tools is essential to ensure protection against newly discovered vulnerabilities and emerging extension-based threats.

Source

https://gbhackers.com/critical-chrome-extension-vulnerabilities/