medium5.1
CVE-2026-27121
Svelte affected by cross-site scripting via spread attributes in Svelte SSR
Impact
Versions of svelte prior to 5.51.5 are vulnerable to cross-site scripting (XSS) during server-side rendering. 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.
Affected packages
| Ecosystem | Package | Affected | Fixed in |
|---|---|---|---|
| npm | svelte | <= 5.51.4 | 5.51.5 |
Affected products
| Vendor | Product | Affected versions |
|---|---|---|
| Svelte | Svelte | before 5.51.5 |