Esbuild version 0.12.6 introduces subtle yet potentially impactful changes compared to the preceding 0.12.5 release. Both versions share the core functionality as an extremely fast JavaScript bundler and minifier, licensed under the MIT license and maintained in the evanw/esbuild GitHub repository. This makes either choice ideal for developers seeking performance optimization in their build processes.
The key difference lies in the unpacked size of the distributed package. Version 0.12.6 boasts a slightly smaller footprint at 88,232 bytes compared to 0.12.5's 89,646 bytes. While seemingly minor, this reduction could translate to marginal improvements in download and installation times, especially within environments with network constraints or frequent package installations during continuous integration.
Furthermore, version 0.12.6 was released on June 4th, 2021, subsequent to version 0.12.5 which arrived on May 28th, 2021. This recency suggests that 0.12.6 incorporates bug fixes, minor optimizations, or dependency updates addressed after the 0.12.5 release. Developers are advised to check the changelog or commit history for precise details on the specific improvements introduced in 0.12.6.
Choosing between the two largely depends on the user’s risk tolerance. Selecting the newer version (0.12.6) grants access to the latest fixes and improvements. If stability is the primary concern, developers should evaluate any potential breaking changes and verify compatibility with their existing project setup before updating. Both versions provide robust bundling and minification capabilities, making esbuild a valuable tool for front-end developers.
All the vulnerabilities related to the version 0.12.6 of the package
esbuild enables any website to send any requests to the development server and read the response
esbuild allows any websites to send any request to the development server and read the response due to default CORS settings.
esbuild sets Access-Control-Allow-Origin: * header to all requests, including the SSE connection, which allows any websites to send any request to the development server and read the response.
https://github.com/evanw/esbuild/blob/df815ac27b84f8b34374c9182a93c94718f8a630/pkg/api/serve_other.go#L121 https://github.com/evanw/esbuild/blob/df815ac27b84f8b34374c9182a93c94718f8a630/pkg/api/serve_other.go#L363
Attack scenario:
http://malicious.example.com).fetch('http://127.0.0.1:8000/main.js') request by JS in that malicious web page. This request is normally blocked by same-origin policy, but that's not the case for the reasons above.http://127.0.0.1:8000/main.js.In this scenario, I assumed that the attacker knows the URL of the bundle output file name. But the attacker can also get that information by
/index.html: normally you have a script tag here/assets: it's common to have a assets directory when you have JS files and CSS files in a different directory and the directory listing feature tells the attacker the list of files/esbuild SSE endpoint: the SSE endpoint sends the URL path of the changed files when the file is changed (new EventSource('/esbuild').addEventListener('change', e => console.log(e.type, e.data)))The scenario above fetches the compiled content, but if the victim has the source map option enabled, the attacker can also get the non-compiled content by fetching the source map file.
npm inpm run watchfetch('http://127.0.0.1:8000/app.js').then(r => r.text()).then(content => console.log(content)) in a different website's dev tools.Users using the serve feature may get the source code stolen by malicious websites.