A critical session isolation vulnerability in the Writer AI platform has been disclosed, allowing an attacker to potentially leak session tokens across tenants. This flaw, codenamed WriteOut, could enable an outsider to gain unauthorized access to sensitive information, potentially taking over any Writer AI instance. The vulnerability is particularly concerning due to its one-click exploitability, making it relatively easy for attackers to compromise the platform. Fortunately, the issue has been patched, mitigating the risk of cross-tenant compromise. The Writer AI platform is an enterprise-grade generative artificial intelligence solution, making the vulnerability's impact potentially significant. The disclosure of this vulnerability highlights the importance of robust session isolation in cloud-based AI platforms1. This matters to security practitioners because it underscores the need for rigorous testing and validation of AI-powered systems to prevent similar vulnerabilities from being exploited.