Storage of File with Sensitive Data Under Web Root

Summary

Astro is a web framework for content-driven websites. A bug in the build process allows any unauthenticated user to read parts of the server source code. During the build, along with client assets such as css and font files, the sourcemap files for the server code are moved to a publicly accessible folder. Any outside party can read them with an unauthorized HTTP GET request to the same server hosting the rest of the website. While some server files are hashed, making their access obscure, the files corresponding to the file system router (those in `src/pages`) are predictably named. For example. the sourcemap file for `src/pages/index.astro` gets named `dist/client/pages/index.astro.mjs.map`. This vulnerability is the root cause of issue #12703, which links to a simple stackblitz project demonstrating the vulnerability. Upon build, notice the contents of the `dist/client` (referred to as `config.build.client` in astro code) folder. All astro servers make the folder in question accessible to the public internet without any authentication. It contains `.map` files corresponding to the code that runs on the server. The immediate impact is limited to source code. Any secrets or environment variables are not exposed unless they are present verbatim in the source code. There is no immediate loss of integrity within the the vulnerable server. However, it is possible to subsequently discover another vulnerability via the revealed source code . There is no immediate impact to availability of the vulnerable server. However, the presence of an unsafe regular expression, for example, can quickly be exploited to subsequently compromise the availability. This issue affects astro versions 4.8.7 through 4.16.17 and 5.0.0-alpha.0 through 5.0.7. Users are advised to update immediately if they are using sourcemaps or an integration that enables sourcemaps.