TLDR: Misconfigured Thymeleaf, introduced in 2011, can lead to vulnerabilities such as cross-site scripting (XSS), data leakage, and code injection. These issues often stem from improper input validation, insecure template settings, and reliance on unsafe defaults, violating several OWASP Top Ten principles, including Output Encoding, Access Controls, and secure Error Handling.
Improper input validation is a significant risk when using Thymeleaf templates. Passing unsanitized or unvalidated user inputs into templates can lead to the rendering of malicious content. This violates the OWASP Top Ten's recommendation for robust Input Validation practices.
https://owasp.org/www-community/Input_Validation
By default, Thymeleaf escapes HTML to protect against XSS. However, developers often bypass this feature using the `th:utext` attribute, which renders raw content. This misuse can allow attackers to inject malicious scripts, breaching the OWASP Top Ten guidelines on Output Encoding.
https://developer.mozilla.org/en-US/docs/Web/Security/Output_Encoding
The use of dynamic fragments in Thymeleaf templates without validation can lead to unauthorized inclusion of files or scripts. This underscores the importance of implementing strict Access Controls and allowlists to prevent unauthorized rendering, as advised by the OWASP Top Ten.
https://www.thymeleaf.org/doc/tutorials/3.0/usingthymeleaf.html#fragments
Exposing sensitive data or configuration variables in Thymeleaf templates without proper encryption or masking increases the risk of data leakage. This violates OWASP Top Ten principles on Data Encryption and secure handling of sensitive information.
https://owasp.org/www-community/Data_Encryption
Inadequate Error Handling in Thymeleaf templates can expose sensitive details, such as variable names or debug information, to attackers. Properly suppressing stack traces and configuring production-safe error messages is critical for aligning with the OWASP Top Ten recommendations.
https://owasp.org/www-community/Error_Handling
Over-reliance on Framework Defaults can leave Thymeleaf applications exposed to vulnerabilities. Developers should review and adjust default configurations to meet specific security requirements, ensuring compliance with the OWASP Top Ten.
https://owasp.org/www-community/Framework_Security_Project
Improper integration of Thymeleaf with API Endpoints can lead to issues with CORS and Cross-Domain Permissions. Unchecked or insecure configurations in Thymeleaf templates can allow unauthorized access or data exposure, violating OWASP Top Ten's Policy Enforcement principles.
https://developer.mozilla.org/en-US/docs/Web/HTTP/CORS
Logging raw inputs or sensitive variables in Thymeleaf templates without encryption can increase exposure risks. Secure Logging practices, such as sanitizing logged data and limiting access to logs, are essential to meet the OWASP Top Ten's recommendations.
https://owasp.org/www-community/Logging_and_Monitoring_Cheat_Sheet
Neglecting regular dependency checking for Thymeleaf and its associated libraries can expose applications to vulnerabilities in outdated components. Tools for alerts for vulnerable components and dependency management are critical for maintaining security, as outlined in the OWASP Top Ten.
https://owasp.org/www-project-dependency-check/
Lastly, remote code execution (RCE) risks in Thymeleaf can arise from untrusted inputs processed through insecure templates. Sandboxing templates and avoiding unverified input usage are essential to prevent such exploits, aligning with the OWASP Top Ten's focus on secure template engine practices.