Svelte 2.1.1 represents a minor update to the Svelte JavaScript framework, building upon version 2.1.0. Both versions share the core philosophy of a "magical disappearing UI framework", emphasizing compile-time transformations rather than runtime overhead for building performant web applications. Comparing the two releases reveals several changes, primarily within the development dependencies, highlighting the ongoing efforts to enhance the developer experience and maintain code quality.
Specifically, newer versions of tools such as eslint, mocha, prettier, typescript and rollup and their respective plugins aimed to improve the code style, unit testing and bundling. Important updates include the upgrade of jsdom which provides a DOM for testing purposes for a better emulation of the real browser, and source-map and its support dependency which are important to debug the generated code. Such upgrades, although invisible at user level, generally bring important bug fixes and performance improvement under the hood.
While the core functionality of Svelte may not have drastically changed, these dependency updates suggest a commitment to leveraging the latest tools and best practices in the JavaScript ecosystem. For developers using Svelte, adopting version 2.1.1 ensures they are working with a slightly more refined development environment, potentially benefiting from improved tooling and a more stable build process. Also, the unpacked size is bigger on the new release, meaning that the team may have added features without documenting it in the description.
All the vulnerabilities related to the version 2.1.1 of the package
Svelte vulnerable to XSS when using objects during server-side rendering
The package svelte before 3.49.0 is vulnerable to Cross-site Scripting (XSS) due to improper input sanitization and to improper escape of attributes when using objects during SSR (Server-Side Rendering). Exploiting this vulnerability is possible via objects with a custom toString() function.
Svelte has a potential mXSS vulnerability due to improper HTML escaping
A potential XSS vulnerability exists in Svelte for versions prior to 4.2.19.
Svelte improperly escapes HTML on server-side rendering. It converts strings according to the following rules:
" -> "& -> &< -> <& -> &The assumption is that attributes will always stay as such, but in some situation the final DOM tree rendered on browsers is different from what Svelte expects on server-side rendering. This may be leveraged to perform XSS attacks. More specifically, this can occur when injecting malicious content into an attribute within a <noscript> tag.
A vulnerable page (+page.svelte):
<script>
import { page } from "$app/stores"
// user input
let href = $page.url.searchParams.get("href") ?? "https://example.com";
</script>
<noscript>
<a href={href}>test</a>
</noscript>
If a user accesses the following URL,
http://localhost:4173/?href=</noscript><script>alert(123)</script>
then, alert(123) will be executed.
XSS, when using an attribute within a noscript tag