CVE-2024-28246

KaTeX is a JavaScript library for TeX math rendering on the web. Code that uses KaTeX's `trust` option, specifically that provides a function to blacklist certain URL protocols, can be fooled by URLs in malicious inputs that use uppercase characters in the protocol. In particular, this can allow for malicious input to generate `javascript:` links in the output, even if the `trust` function tries to forbid this protocol via `trust: (context) => context.protocol !== 'javascript'`. Upgrade to KaTeX v0.16.10 to remove this vulnerability.

KaTeX is a JavaScript library for TeX math rendering on the web. Code that uses KaTeX's `trust` option, specifically that provides a function to blacklist certain URL protocols, can be fooled by URLs in malicious inputs that use uppercase characters in the protocol. In particular, this can allow for malicious input to generate `javascript:` links in the output, even if the `trust` function tries to forbid this protocol via `trust: (context) => context.protocol !== 'javascript'`. Upgrade to KaTeX v0.16.10 to remove this vulnerability.

### Impact Code that uses KaTeX's `trust` option, specifically that provides a function to block-list certain URL protocols, can be fooled by URLs in malicious inputs that use uppercase characters in the protocol. In particular, this can allow for malicious input to generate `javascript:` links in the output, even if the `trust` function tries to forbid this protocol via `trust: (context) => context.protocol !== 'javascript'`. ### Patches Upgrade to KaTeX v0.16.10 to remove this vulnerability. ### Workarounds * Allow-list instead of block protocols in your `trust` function. * Manually lowercase `context.protocol` via `context.protocol.toLowerCase()` before attempting to check for certain protocols. * Avoid use of or turn off the `trust` option. ### Details KaTeX did not normalize the `protocol` entry of the `context` object provided to a user-specified `trust`-function, so it could be a mix of lowercase and/or uppercase letters. It is generally better to allow-list by protocol, in which case this would normally not be an issue. But in some cases, you might want to block-list, and the [KaTeX documentation](https://katex.org/docs/options.html) even provides such an example: > Allow all commands but forbid specific protocol: `trust: (context) => context.protocol !== 'file'` Currently KaTeX internally sees `file:` and `File:` URLs as different protocols, so `context.protocol` can be `file` or `File`, so the above check does not suffice. A simple workaround would be: > `trust: (context) => context.protocol.toLowerCase() !== 'file'` Most URL parsers normalize the scheme to lowercase. For example, [RFC3986](https://datatracker.ietf.org/doc/html/rfc3986#section-3.1) says: > Although schemes are case-insensitive, the canonical form is lowercase and documents that specify schemes must do so with lowercase letters. An implementation should accept uppercase letters as equivalent to lowercase in scheme names (e.g., allow "HTTP" as well as "http") for the sake of robustness but should only produce lowercase scheme names for consistency.

### Impact Code that uses KaTeX's `trust` option, specifically that provides a function to block-list certain URL protocols, can be fooled by URLs in malicious inputs that use uppercase characters in the protocol. In particular, this can allow for malicious input to generate `javascript:` links in the output, even if the `trust` function tries to forbid this protocol via `trust: (context) => context.protocol !== 'javascript'`. ### Patches Upgrade to KaTeX v0.16.10 to remove this vulnerability. ### Workarounds * Allow-list instead of block protocols in your `trust` function. * Manually lowercase `context.protocol` via `context.protocol.toLowerCase()` before attempting to check for certain protocols. * Avoid use of or turn off the `trust` option. ### Details KaTeX did not normalize the `protocol` entry of the `context` object provided to a user-specified `trust`-function, so it could be a mix of lowercase and/or uppercase letters. It is generally better to allow-list by protocol, in which case this would normally not be an issue. But in some cases, you might want to block-list, and the [KaTeX documentation](https://katex.org/docs/options.html) even provides such an example: > Allow all commands but forbid specific protocol: `trust: (context) => context.protocol !== 'file'` Currently KaTeX internally sees `file:` and `File:` URLs as different protocols, so `context.protocol` can be `file` or `File`, so the above check does not suffice. A simple workaround would be: > `trust: (context) => context.protocol.toLowerCase() !== 'file'` Most URL parsers normalize the scheme to lowercase. For example, [RFC3986](https://datatracker.ietf.org/doc/html/rfc3986#section-3.1) says: > Although schemes are case-insensitive, the canonical form is lowercase and documents that specify schemes must do so with lowercase letters. An implementation should accept uppercase letters as equivalent to lowercase in scheme names (e.g., allow "HTTP" as well as "http") for the sake of robustness but should only produce lowercase scheme names for consistency.

KaTeX es una librería de JavaScript para la representación matemática de TeX en la web. El código que utiliza la opción `trust` de KaTeX, específicamente el que proporciona una función para incluir en la lista negra ciertos protocolos URL, puede ser engañado por URL en entradas maliciosas que utilizan caracteres en mayúsculas en el protocolo. En particular, esto puede permitir que entradas maliciosas generen enlaces `javascript:` en la salida, incluso si la función `trust` intenta prohibir este protocolo mediante `trust: (context) => context.protocol !== 'javascript' `. Actualice a KaTeX v0.16.10 para eliminar esta vulnerabilidad.