i18nextify is vulnerable to DOM XSS via javascript:/data: URL schemes in translated href/src attributes

i18nextify is a JavaScript library that adds website internationalization via a script tag, without source code changes. Versions prior to 4.0.8 substitute {{key}} interpolation tokens inside src and href attribute values with the raw string returned by i18next.t(). The substitution logic in src/localize.js (the replaceInside handler) only guards against a duplicated http:// origin prefix — it does not validate the URL scheme of the substituted value. A translated value such as javascript:alert(1) or data:text/html,<script>...</script> is applied unchanged to the live DOM attribute when an attacker can influence the content of a translation file or the translation-backend response — for example, via a compromised translation CDN, user-contributed locales, a MITM on a plain-HTTP backend, or write access to the translation JSON. This issue was patched in version 4.0.8.

Source published

7 May 2026 20:01:59 UTC

Source modified

11 May 2026 18:04:43 UTC

Observed here

23 Oct 2026 15:48:27 UTC

Source terms

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CVSS 3.1 · 4.7 CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:C/C:L/I:L/A:N