Svelte version 3.42.5, released on September 10, 2021, is a minor update to the popular Svelte JavaScript compiler, succeeding version 3.42.4, which was released on August 27, 2021. While both versions share the same core description of "Cybernetically enhanced web apps", indicating a focus on performance and developer experience, a closer look reveals subtle differences. The dependency list remains identical, encompassing tools for testing (Mocha, jsdom, c8), linting (eslint), bundling (Rollup), and TypeScript support. This suggests that the update isn't centered on radically changing the development environment or tooling.
The most notable difference lies in the unpacked size of the distribution. Version 3.42.5 weighs in at 6,932,426 bytes, a slight increase from version 3.42.4's 6,930,694 bytes. This increment, approximately 1.7 kilobytes, likely reflects bug fixes, performance tweaks, or minor feature additions within the compiler itself. Developers may not directly interact with these changes but should expect improved stability or subtle performance enhancements.
For developers considering upgrading, this update represents a low-risk proposition. The identical dependency structure means no compatibility issues are anticipated with existing projects. The slightly larger size suggests internal improvements rather than breaking API changes. Given the focus on developer experience inherent in Svelte's design, this update likely delivers a smoother and more efficient development process, further solidifying Svelte as a compelling choice for building modern web applications.
All the vulnerabilities related to the version 3.42.5 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