Reflected XSS in go-httpbin due to unrestricted client control over Content-Type

Description

The go-httpbin framework is vulnerable to XSS as the user can control the Response Content-Type from GET parameter. This allows attacker to execute cross site scripts in victims browser.

Affected URLs:

• /response-headers?Content-Type=text/html&xss=%3Cimg/src/onerror=alert(%27xss%27)%3E
• /base64/PGltZy9zcmMvb25lcnJvcj1hbGVydCgneHNzJyk+?content-type=text/html
• /base64/decode/PGltZy9zcmMvb25lcnJvcj1hbGVydCgneHNzJyk+?content-type=text/html

Steps to reproduce:

1. Visit one of the above mentioned URLs.
2. XSS window will popup

Suggested fix

• Allow Only Safe Content-Type Values Or give users option to define whitelisted Content-Type headers

Criticality

The following can be major impacts of the issue:

• Access to victim's sensitive Personal Identifiable Information.
• Access to CSRF token
• Cookie injection
• Phishing
• And any other thing Javascript can perform