Highlight.js is a widely used syntax highlighting library for the web, automatically detecting languages and providing attractive code formatting. Comparing versions 9.12.0 and 9.11.0, developers will find that the core functionality and developer dependencies remain consistent. Both versions utilize the same suite of tools for development, including del, gear, glob, jsdom, mocha, lodash, should, bluebird, gear-lib, commander, js-beautify, and tiny-worker, indicating a stable development environment and consistent build process. The primary difference lies in the release date and the associated package distribution. Version 9.12.0 was released on May 31, 2017, while version 9.11.0 was released on April 19, 2017. This suggests that version 9.12.0 likely includes bug fixes, minor improvements, and potential updates to language definitions or highlighting rules accumulated during that roughly six-week period. For developers using Highlight.js, upgrading from 9.11.0 to 9.12.0 is recommended to benefit from the latest refinements and ensure optimal code highlighting. The consistent dependency structure means upgrading should pose minimal risk and can provide a more polished user experience. Check the official Highlight.js release notes or commit history for a detailed list of specific changes between the two versions.
All the vulnerabilities related to the version 9.12.0 of the package
Prototype Pollution in highlight.js
Affected versions of this package are vulnerable to Prototype Pollution. A malicious HTML code block can be crafted that will result in prototype pollution of the base object's prototype during highlighting. If you allow users to insert custom HTML code blocks into your page/app via parsing Markdown code blocks (or similar) and do not filter the language names the user can provide you may be vulnerable.
The pollution should just be harmless data but this can cause problems for applications not expecting these properties to exist and can result in strange behavior or application crashes, i.e. a potential DOS vector.
If your website or application does not render user provided data it should be unaffected.
Versions 9.18.2 and 10.1.2 and newer include fixes for this vulnerability. If you are using version 7 or 8 you are encouraged to upgrade to a newer release.
Manually patch your library to create null objects for both languages and aliases:
const HLJS = function(hljs) {
// ...
var languages = Object.create(null);
var aliases = Object.create(null);
Filter the language names that users are allowed to inject into your HTML to guarantee they are valid.
If you have any questions or comments about this advisory:
ReDOS vulnerabities: multiple grammars
The Regular expression Denial of Service (ReDoS) is a Denial of Service attack, that exploits the fact that most Regular Expression implementations may reach extreme situations that cause them to work very slowly (exponentially related to input size). An attacker can then cause a program using a Regular Expression to enter these extreme situations and then hang for a very long time.
If are you are using Highlight.js to highlight user-provided data you are possibly vulnerable. On the client-side (in a browser or Electron environment) risks could include lengthy freezes or crashes... On the server-side infinite freezes could occur... effectively preventing users from accessing your app or service (ie, Denial of Service).
This is an issue with grammars shipped with the parser (and potentially 3rd party grammars also), not the parser itself. If you are using Highlight.js with any of the following grammars you are vulnerable. If you are using highlightAuto to detect the language (and have any of these grammars registered) you are vulnerable. Exponential grammars (C, Perl, JavaScript) are auto-registered when using the common grammar subset/library require('highlight.js/lib/common') as of 10.4.0 - see https://cdn.jsdelivr.net/gh/highlightjs/cdn-release@10.4.0/build/highlight.js
All versions prior to 10.4.1 are vulnerable, including version 9.18.5.
Grammars with exponential backtracking issues:
And of course any aliases of those languages have the same issue. ie: hpp is no safer than cpp.
Grammars with polynomial backtracking issues:
And again: any aliases of those languages have the same issue. ie: ruby and rb share the same ruby issues.
If you have any questions or comments about this advisory: