Svelte SSR vulnerable to cross-site scripting via spread attributes
Published 14 May 2026 · Updated 9 Jun 2026
Affected package
- Affected
- <5.55.7
- Fixed in
- 5.55.7
npm install svelte@5.55.7Details
When using spread syntax to render attributes from untrusted data, event handler properties are included in the rendered HTML output. If an application spreads user-controlled or external data as element attributes, an attacker can inject malicious event handlers that execute in victims' browsers. Note that this vulnerability _only_ triggers if the user's browser has JavaScript enabled but Svelte's hydration mechanism does not reach the vulnerable element before the event fires.
This is similar to but different from CVE-2026-27121.
Is GHSA-pr6f-5x2q-rwfp in any of your client repos?
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References
Advisory data from OSV.dev (opens OSV.dev in a new tab), refreshed daily.