{"id":"GHSA-f3cj-j4f6-wq85","summary":"Svelte: SSR XSS via Insecure Promise Serialization in hydratable","details":"Contents of `hydratable` promises were not properly stringified, potentially leading to an XSS exploit. You are vulnerable if all of the following is true:\n- you are using `hydratable` (an experimental feature at the time of this report)\n- you are passing attacker-controlled input such that a synchronous value is hydrated, then a promise value, e.g. `hydratable('someKey', () =\u003e [synchronousValue, promiseValue])`","modified":"2026-05-14T20:49:54.154680Z","published":"2026-05-14T20:30:09Z","database_specific":{"nvd_published_at":null,"cwe_ids":["CWE-79"],"severity":"MODERATE","github_reviewed":true,"github_reviewed_at":"2026-05-14T20:30:09Z"},"references":[{"type":"WEB","url":"https://github.com/sveltejs/svelte/security/advisories/GHSA-f3cj-j4f6-wq85"},{"type":"WEB","url":"https://github.com/sveltejs/svelte/commit/a16ebc67bbcf8f708360195687e1b2719463e1a4"},{"type":"PACKAGE","url":"https://github.com/sveltejs/svelte"},{"type":"WEB","url":"http://github.com/sveltejs/svelte/releases/tag/svelte%405.55.7"}],"affected":[{"package":{"name":"svelte","ecosystem":"npm","purl":"pkg:npm/svelte"},"ranges":[{"type":"SEMVER","events":[{"introduced":"5.46.0"},{"fixed":"5.55.7"}]}],"database_specific":{"last_known_affected_version_range":"\u003c= 5.55.6","source":"https://github.com/github/advisory-database/blob/main/advisories/github-reviewed/2026/05/GHSA-f3cj-j4f6-wq85/GHSA-f3cj-j4f6-wq85.json"}}],"schema_version":"1.9.0","severity":[{"type":"CVSS_V4","score":"CVSS:4.0/AV:N/AC:L/AT:P/PR:L/UI:N/VC:N/VI:N/VA:N/SC:H/SI:H/SA:N"}]}