Esbuild version 0.7.19 represents a minor update over its predecessor, version 0.7.18, in the rapidly evolving world of JavaScript bundlers. Both versions maintain the core promise of esbuild: providing an extremely fast bundling and minification solution for JavaScript projects. The fundamental characteristics, such as the MIT license and the source code repository on GitHub, remain unchanged between the two versions, ensuring continued open-source access and community collaboration.
The most noticeable difference lies in the updated release date, with version 0.7.19 being published on October 21, 2020, roughly a day after version 0.7.18. This suggests that the newer version likely includes bug fixes, minor performance improvements, or small feature enhancements discovered shortly after the release of 0.7.18. The slight increase in unpacked size, from 39554 to 39691, further corroborates this, indicating the addition of new code or adjustments to existing code.
Developers considering esbuild should note that both versions offer the core benefits of speed and efficiency. The choice between 0.7.18 and 0.7.19 hinges on whether the specific fixes or enhancements included in the latter are relevant to their project. Checking the changelog or release notes associated with version 0.7.19 will provide detailed information about the changes made, allowing developers to make an informed decision regarding which version best suits their needs. The small increment suggests a low-risk update guaranteeing faster builds and optimized output, especially valuable for large and complex JavaScript applications. Ultimately, esbuild empowers developers to streamline their build processes and deliver performant web applications.
All the vulnerabilities related to the version 0.7.19 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.