All versions of the package github.com/greenpau/caddy-security are vulnerable to Cross-site Scripting (XSS) via the Referer header, due to improper input sanitization. Although the Referer header is sanitized by escaping some characters that can allow XSS (e.g., [&], [<], [>], ["], [']), it does not account for the attack based on the JavaScript URL scheme (e.g., javascript:alert(document.domain)// payload). Exploiting this vulnerability may not be trivial, but it could lead to the execution of malicious scripts in the context of the target user’s browser, compromising user sessions.

References

• https://nvd.nist.gov/vuln/detail/CVE-2024-21496
• greenpau/caddy-security#267
• https://blog.trailofbits.com/2023/09/18/security-flaws-in-an-sso-plugin-for-caddy
• https://security.snyk.io/vuln/SNYK-GOLANG-GITHUBCOMGREENPAUCADDYSECURITY-6249860