Babel Preset React App version 9.1.2 introduces key updates and improvements for React developers, building upon the foundation of version 9.1.1. The most significant change lies in the updated dependencies. Version 9.1.2 upgrades several core Babel packages, including @babel/core, @babel/runtime, @babel/preset-env, @babel/preset-react, @babel/preset-typescript, @babel/plugin-transform-runtime, and @babel/plugin-proposal-optional-chaining to version 7.9.0 or 7.9.1. Furthermore, it introduces the @babel/plugin-proposal-nullish-coalescing-operator as a dependency at version 7.8.3.
These upgrades bring enhanced support for the latest JavaScript and React features, ensuring better compatibility and performance. The inclusion of the nullish coalescing operator plugin allows developers to use the ?? operator, providing a concise way to handle default values when dealing with null or undefined. The updated preset-react package ensures compatibility with the latest React syntax. Developers upgrading from 9.1.1 should be aware of potential minor behavioral changes introduced by these Babel updates, although they are generally aimed at improving standard compliance and adding new features. Essentially, 9.1.2 offers a more up-to-date Babel environment, equipping developers with the tools needed to efficiently develop modern React applications. The increased unpacked size, from 19429 to 20009, reflects these added features and dependency updates.
All the vulnerabilities related to the version 9.1.2 of the package
Babel has inefficient RegExp complexity in generated code with .replace when transpiling named capturing groups
When using Babel to compile regular expression named capturing groups, Babel will generate a polyfill for the .replace method that has quadratic complexity on some specific replacement pattern strings (i.e. the second argument passed to .replace).
Your generated code is vulnerable if all the following conditions are true:
.replace method on a regular expression that contains named capturing groups.replaceIf you are using @babel/preset-env with the targets option, the transform that injects the vulnerable code is automatically enabled if:
You can verify what transforms @babel/preset-env is using by enabling the debug option.
This problem has been fixed in @babel/helpers and @babel/runtime 7.26.10 and 8.0.0-alpha.17, please upgrade. It's likely that you do not directly depend on @babel/helpers, and instead you depend on @babel/core (which itself depends on @babel/helpers). Upgrading to @babel/core 7.26.10 is not required, but it guarantees that you are on a new enough @babel/helpers version.
Please note that just updating your Babel dependencies is not enough: you will also need to re-compile your code.
If you are passing user-provided strings as the second argument of .replace on regular expressions that contain named capturing groups, validate the input and make sure it does not contain the substring $< if it's then not followed by > (possibly with other characters in between).
This vulnerability was reported and fixed in https://github.com/babel/babel/pull/17173.