Babel-preset-react-app is a crucial tool for Create React App projects, handling the transformation of modern JavaScript and JSX code into browser-compatible formats. Version 9.1.1, released on January 31, 2020, includes significant updates compared to the prior stable version 9.1.0, released on December 5, 2019. A primary difference lies in the updated dependencies. Version 9.1.1 upgrades several core Babel packages, incorporating @babel/core, @babel/runtime, @babel/preset-env, @babel/preset-react, @babel/preset-typescript and @babel/plugin-transform-runtime to versions 7.8.4 and 7.8.3 from 7.7.4. This likely brings performance improvements, bug fixes, and support for newer JavaScript features. Several plugins present in version 9.1.0 like babel-plugin-dynamic-import-node, @babel/plugin-syntax-dynamic-import, @babel/plugin-transform-destructuring, @babel/plugin-proposal-optional-chaining, @babel/plugin-proposal-object-rest-spread and @babel/plugin-proposal-nullish-coalescing-operator are not present in the newer version. While babel-plugin-macros has been updated to version 2.8.0 from 2.7.1. Developers upgrading to 9.1.1 can expect benefits from the enhanced Babel core, potentially leading to faster build times and better compatibility. The reduced unpacked size in version 9.1.1 may also indicate a lighter footprint. However, the removed plugins might require developers to manually add them in certain use cases. It's essential to review the specific changes in Babel's core packages to fully understand the implications of this upgrade for your React application.
All the vulnerabilities related to the version 9.1.1 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.