Errors from transformError were not correctly escaped prior to being embedded in the HTML output, causing potential HTML injection and XSS if attacker-controlled content is returned from transformError.

Svelte performance oriented web framework. Prior to version 5.53.5, the contents of bind:innerText and bind:textContent on contenteditable elements were not properly escaped. This could enable HTML injection and Cross-Site Scripting (XSS) if rendering untrusted data as the binding's initial value on the server. Version 5.53.5 fixes the issue.

The package svelte before 3.49.0 are 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.