Researchers have discovered a vulnerability in Cursor, an AI-powered coding tool, where a malicious MCP (Managed Code Platform) server can hijack Cursor's internal browser. Cursor integrates an internal browser component to facilitate various functionalities, but this integration introduces a security weakness. The malicious MCP server can exploit this weakness to gain control over the internal browser, potentially allowing attackers to steal user credentials and other sensitive data processed within the tool. The vulnerability arises from insufficient isolation and validation between Cursor and the MCP server communications, enabling hijacking of browser sessions. Although the affected versions are unspecified and no patches or known exploits are currently reported, the risk lies in the potential for attackers to intercept authentication tokens, session cookies, or input data. This could lead to unauthorized access to development environments, source code repositories, or other integrated services. The low reported severity may reflect the current difficulty of exploitation or limited impact scope, but credential theft remains a critical concern. The attack vector requires a malicious MCP server, which could be introduced via supply chain compromise or insider threat. This vulnerability highlights the risks of integrating complex internal browsers within development tools without robust security controls.

For European organizations, especially those heavily reliant on AI-assisted coding tools like Cursor, this vulnerability could lead to unauthorized credential theft, compromising access to critical development environments and intellectual property. The confidentiality of sensitive project data and user credentials is at risk, potentially enabling further lateral movement within corporate networks. This could disrupt software development workflows, delay project timelines, and damage organizational reputation. Given the increasing adoption of AI coding assistants in Europe’s technology sector, the threat could affect a broad range of companies from startups to large enterprises. Additionally, compromised credentials might be leveraged to access cloud services, internal repositories, or CI/CD pipelines, amplifying the impact. While the current severity is low, the potential for escalation exists if attackers combine this vulnerability with other exploits. The absence of known exploits suggests a window for proactive defense, but organizations must remain vigilant to prevent supply chain or insider threats that could introduce malicious MCP servers.

Organizations should implement strict validation and authentication mechanisms for MCP servers interacting with Cursor to prevent unauthorized or malicious servers from gaining control. Network segmentation should isolate development tools like Cursor from sensitive production environments to limit lateral movement in case of compromise. Monitoring and logging of Cursor’s internal browser activities can help detect anomalous behavior indicative of hijacking attempts. Until official patches are released, consider restricting or disabling the internal browser feature if feasible, or running Cursor in a sandboxed environment with limited privileges. Educate developers and IT staff about the risks of supply chain attacks and enforce strict controls over third-party integrations. Employ multi-factor authentication and credential vaulting to reduce the impact of stolen credentials. Regularly update and audit all components related to Cursor and MCP servers. Collaborate with Cursor’s vendor for timely security updates and guidance.