Svelte is a radical approach to building user interfaces, shifting the workload from the browser to compile time, resulting in highly performant and lightweight web applications. Comparing versions 1.3.0 and 1.3.1 reveals a minor update, but even small changes can be significant for developers. Both versions share the same core philosophy and dependencies, including magic-string for efficient string manipulation during compilation. They also have identical development dependencies, encompassing tools for testing (mocha, jsdom, nyc), linting (eslint), module bundling (rollup), code coverage (codecov), and various utilities for AST traversal, source map handling, and Babel transformations.
The most apparent difference lies in the releaseDate. Version 1.3.1 was published just a few hours after 1.3.0. Therefore the changes were likely bug fixes and could also be performance improvements aimed at refining the developer and user experience. Developers should check Svelte's change log for a detailed explanation of what was updated. Typically, patch updates address critical issues without introducing breaking changes. Svelte focuses on producing optimized JavaScript during compilation, offering a faster, leaner alternative to traditional virtual DOM frameworks. Therefore, the impact of this patch might be noticeable in more complex applications, especially those with many dynamic components. Developers should update to the newest version to ensure that they are using the most stable version of Svelte.
All the vulnerabilities related to the version 1.3.1 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