Anubis is a Web AI Firewall Utility that weighs the soul of users connections using one or more challenges in order to protect upstream resources from scraper bots. In versions 1.21.2 and below, attackers can craft malicious pass-challenge pages that cause a user to execute arbitrary JavaScript code or trigger other nonstandard schemes. An incomplete version of this fix was tagged at 1.21.2 and then the release process was aborted upon final testing. To work around this issue: block any requests to the /.within.website/x/cmd/anubis/api/pass-challenge route with the ?redir= parameter set to anything that doesnt start with the URL scheme http, https, or no scheme (local path redirect). This was fixed in version 1.21.3.
Weakness
The product receives input from an upstream component, but it does not neutralize or incorrectly neutralizes special characters such as “<”, “>”, and “&” that could be interpreted as web-scripting elements when they are sent to a downstream component that processes web pages.
Potential Mitigations
- Use and specify an output encoding that can be handled by the downstream component that is reading the output. Common encodings include ISO-8859-1, UTF-7, and UTF-8. When an encoding is not specified, a downstream component may choose a different encoding, either by assuming a default encoding or automatically inferring which encoding is being used, which can be erroneous. When the encodings are inconsistent, the downstream component might treat some character or byte sequences as special, even if they are not special in the original encoding. Attackers might then be able to exploit this discrepancy and conduct injection attacks; they even might be able to bypass protection mechanisms that assume the original encoding is also being used by the downstream component.
- The problem of inconsistent output encodings often arises in web pages. If an encoding is not specified in an HTTP header, web browsers often guess about which encoding is being used. This can open up the browser to subtle XSS attacks.
References