If user-supplied input was passed into
append/override_content_security_policy_directives, a semicolon could be injected leading to directive injection.
This could be used to e.g. override a
script-src directive. Duplicate directives are ignored and the first one wins. The directives in
secure_headers are sorted alphabetically so they pretty much all come before
script-src. A previously undefined directive would receive a value even if
SecureHeaders::OPT_OUT was supplied.
The fixed versions will silently convert the semicolons to spaces and emit a deprecation warning when this happens. This will result in innocuous browser console messages if being exploited/accidentally used. In future releases, we will raise application errors resulting in 500s.
Duplicate script-src directives detected. All but the first instance will be ignored.
Note: In this case, the user agent SHOULD notify developers that a duplicate directive was ignored. A console warning might be appropriate, for example.
Depending on what major version you are using, the fixed versions are 6.2.0, 5.1.0, 3.8.0.
If you are passing user input into the above methods, you could filter out the input:
override_content_security_policy_directives(:frame_src, [user_input.gsub(";", " ")])
Reported in https://github.com/twitter/secure_headers/issues/418 https://www.w3.org/TR/CSP3/#parse-serialized-policy
If you have any questions or comments about this advisory: * Open an issue in this repo * DM @ndm on twitter