PostMessaged and Compromised
15 days ago
- #Microsoft
- #security
- #postMessage
- Microsoft focuses on proactive security measures, including identifying systemic weaknesses and mitigating risks before exploitation.
- postMessage API is crucial for secure cross-origin communication but can become a vulnerability if origin validation is misconfigured.
- Common postMessage vulnerabilities include insecure senders and listeners, leading to token theft, XSS, and privilege escalation.
- Validating window objects instead of origins in postMessage can create security loopholes, allowing attackers to hijack iframes.
- Case studies highlight vulnerabilities like auth token exposure in Bing Travel and web.kusto.windows.net due to wildcard targetOrigin.
- Overly broad origin validation in services like Microsoft 365, Azure, and Dynamics 365 can lead to token theft and unauthorized actions.
- Exploitation techniques include XSS in trusted domains, taking over dangling domains, and leveraging custom code in platforms like Power Apps.
- Teams apps with overly permissive manifest settings (isFullTrust: true, broad validDomains) are particularly vulnerable to postMessage attacks.
- Mitigation strategies include strict origin validation, removing wildcard domains, and enforcing Content Security Policy (CSP) headers.
- Microsoft's response to CVE-2024-49038 involved updating app manifests, removing wildcard entries, and enforcing secure-by-default configurations.
- Customers are advised to audit app manifests, limit privileges, and use tools like CodeQL to detect insecure postMessage patterns.