SvelteKit is a framework for rapidly developing robust, performant web applications using Svelte. The static error.html template for errors contains placeholders that are replaced without escaping the content first. error.html is the page that is rendered when everything else fails. It can contain the following placeholders: %sveltekit.status% — the HTTP status, and %sveltekit.error.message% — the error message. This leads to possible injection if an app explicitly creates an error with a message that contains user controlled content. Only applications where user provided input is used in the `Error` message will be vulnerable, so the vast majority of applications will not be vulnerable This issue has been addressed in version 2.8.3 and all users are advised to upgrade. There are no known workarounds for this vulnerability.

SvelteKit is a framework for rapidly developing robust, performant web applications using Svelte. "Unsanitized input from *the request URL* flows into `end`, where it is used to render an HTML page returned to the user. This may result in a Cross-Site Scripting attack (XSS)." The files `packages/kit/src/exports/vite/dev/index.js` and `packages/kit/src/exports/vite/utils.js` both contain user controllable data which under specific conditions may flow to dev mode pages. There is little to no expected impact. The Vite development is not exposed to the network by default and even if someone were able to trick a developer into executing an XSS against themselves, a development database should not have any sensitive data. None the less this issue has been addressed in version 2.8.3 and all users are advised to upgrade.