Esbuild, a lightning-fast JavaScript bundler and minifier, released version 0.12.3 shortly after version 0.12.2. Both versions share the same core characteristics: MIT license, hosted on GitHub under the evanw/esbuild repository, and boasting a compact footprint with an unpacked size of 88,232 bytes across 6 files. Developers familiar with esbuild will find the setup and integration process consistent between the two.
The key difference lies in timing. Version 0.12.3 was published on May 26, 2021, while version 0.12.2 appeared just a day earlier on May 25, 2021. This suggests that version 0.12.3 likely contains bug fixes or minor enhancements addressing issues discovered shortly after the release of 0.12.2. Developers contemplating a new esbuild integration should strongly consider opting for version 0.12.3 to benefit from these potential immediate improvements, as it represents the most recent stable release at that point in time.
While the package size and core functionality seemingly remain the same based on the provided information, upgrading ensures access to the latest refinements. Always choosing the newest version is a good security and best-practice development model. Both versions are available through the npm registry, accessible via their respective tarball URLs, making installation a breeze for developers already using npm in their projects.
All the vulnerabilities related to the version 0.12.3 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.