Misconfigured EJS
TLDR: Misconfigured EJS (Embedded JavaScript Templates), introduced in 2010, often leads to vulnerabilities such as cross-site scripting (XSS), code injection, and data leakage. These issues arise from improper input handling, insecure template configurations, and reliance on unsafe defaults, violating several OWASP Top Ten principles such as Input Validation, Output Encoding, and Access Controls.
Improper input validation is a key issue when using EJS. Passing unsanitized user inputs directly into templates can allow attackers to inject malicious scripts or manipulate outputs. This misconfiguration violates the OWASP Top Ten's recommendation for robust Input Validation practices.
https://owasp.org/www-community/Input_Validation
Disabling or bypassing EJS's built-in escaping mechanisms exposes templates to XSS attacks. Developers often misuse the `<%- %>` syntax, which renders unescaped content, allowing malicious JavaScript to execute. Adhering to proper Output Encoding techniques is crucial to mitigate these risks.
https://developer.mozilla.org/en-US/docs/Web/Security/Output_Encoding
Unrestricted use of dynamic includes in EJS templates can lead to the inclusion of untrusted files or scripts. This practice highlights the need for strict Access Controls and allowlists, aligning with the OWASP Top Ten's guidance on preventing unauthorized resource access.
Exposing sensitive data or configuration variables directly in EJS templates without proper masking or encryption increases the risk of data leakage. This behavior violates OWASP Top Ten's principles on Data Encryption and secure data handling.
https://owasp.org/www-community/Data_Encryption
Failing to properly handle error messages in EJS templates can reveal sensitive information, such as application architecture or debug data. This issue underlines the importance of masking stack traces and ensuring secure Error Handling in production environments, as advised by the OWASP Top Ten.
https://owasp.org/www-community/Error_Handling
Over-reliance on EJS's Framework Defaults often results in uncustomized configurations that may not align with specific security requirements. Developers should review and harden default settings to reduce risks, as highlighted in the OWASP Top Ten.
https://owasp.org/www-community/Framework_Security_Project
When integrating EJS templates with API Endpoints, failing to enforce CORS or secure Cross-Domain Permissions can lead to unauthorized access or embedding. The OWASP Top Ten emphasizes strict Policy Enforcement to avoid these vulnerabilities.
https://developer.mozilla.org/en-US/docs/Web/HTTP/CORS
Improper handling of logging within EJS templates can result in sensitive data being stored insecurely. Logging raw inputs or sensitive variables without encryption increases exposure risks, violating OWASP Top Ten recommendations on secure Logging and monitoring.
https://owasp.org/www-community/Logging_and_Monitoring_Cheat_Sheet
EJS templates that fail to validate helper functions or external scripts risk introducing vulnerabilities through untrusted dependencies. Regular dependency checking and alerts for vulnerable components are essential to maintaining secure template engine configurations, as per the OWASP Top Ten.
https://owasp.org/www-project-dependency-check/
Lastly, developers must address the potential for remote code execution (RCE) in EJS by sandboxing untrusted input and avoiding unnecessary use of dynamic expressions. This aligns with the OWASP Top Ten's focus on securing template engine environments.