Svelte 1.21.0 marks a minor version update to the "magical disappearing UI framework," building upon the foundation laid by version 1.20.2. While both versions share the same core description, license (MIT), repository, and author (Rich Harris), indicating a consistent project philosophy and maintainership, the key difference lies in the release date and potentially internal improvements. Svelte 1.21.0 was released on May 28, 2017, whereas version 1.20.2 was released earlier on May 6, 2017.
For developers using Svelte, this update likely incorporates bug fixes and minor performance enhancements accumulated during those weeks. While the devDependencies field remains largely the same, suggesting no major shifts in the build or testing process, a closer examination of the Svelte changelog (available via the Svelte repository) would reveal the precise changes included.
Developers upgrading from 1.20.2 to 1.21.0 should anticipate a smooth transition. Focus will be on enhanced stability and potential edge-case resolution. Existing code written for 1.20.2 should ideally function without modification in 1.21.0 due to the nature of minor version upgrades. If you are seeking the latest features and improvements, always prefer the latest stable version of the framework. Svelte is known for its compiler approach, which translates code into highly optimized Vanilla Javascript during build time making it an excellent option for performant web applications. Always refer to official Svelte documentation for detailed upgrade instructions and new features.
All the vulnerabilities related to the version 1.21.0 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