| Package | Affected versions | Patched versions |
|---|---|---|
| svelte | ≥ 5.46.0, < 5.46.3 | 5.46.3 |
| svelte | ≥ 5.46.0, < 5.46.4 | 5.46.4 |
An XSS vulnerability exists in Svelte 5.46.0-2 resulting from improper escaping of hydratable keys. If these keys incorporate untrusted user input, arbitrary JavaScript can be injected into server-rendered HTML.
When using the hydratable function, the first argument is used as a key to uniquely identify the data, such that the value is not regenerated in the browser.
This key is embedded into a <script> block in the server-rendered <head> without escaping unsafe characters. A malicious key can break out of the script context and inject arbitrary JavaScript into the HTML response.
This is a cross-site scripting vulnerability affecting applications that have the experimental.async flag enabled and use hydratable with keys incorporating untrusted user input.
Affected applications should upgrade to a patched version immediately.
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