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

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No collected risk observation for these identifiers. This does not establish absence of exploitation or a zero probability.

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

CVE Program Terms of Use

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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

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

May 7, 2026, 8:01:59 PM (timezone not stated)

Source modified

May 11, 2026, 6:04:43 PM (timezone not stated)

Observed here

1 Nov 2026 23:05:12 UTC

Source terms

ENISA EUVD · source terms and attribution apply

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

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 21:16:29 UTC

Source modified

26 Oct 2026 20:10:00 UTC

Observed here

27 Oct 2026 10:10:19 UTC

Source terms

NIST NVD usage terms; underlying source attribution retained

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This view projects the publisher's source fields for reading; the original JSON retains additional fields and CVE enrichment containers. Attribution: nvd · NIST NVD usage terms; underlying source attribution retained. Source text is retained; field grouping and change labels are provided by ChangeIntel.

CVSS 3.1 · [email protected] · Secondary · 4.7 CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:C/C:L/I:L/A:N

CVSS 3.1 · [email protected] · Primary · 4.7 CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:C/C:L/I:L/A:N

### Summary Versions of `i18nextify` 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` (`replaceInside` handler around line 122) 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. ### Impact When an attacker can influence the content of a translation file or the translation-backend response — compromised translation CDN, user-contributed locales, MITM on a plain-HTTP backend, write access to the translation JSON — they can: - Set any `href` on an anchor to a `javascript:` URI, executing arbitrary JavaScript when the victim clicks the link. - Set any `src` on `<iframe>`, `<object>`, or `<embed>` to a `data:text/html` URI containing a full script payload that runs in the page's origin. - Use `vbscript:` on legacy IE installations or `file:` for local-resource navigation attacks. This path is distinct from the general i18nextify design that intentionally renders HTML from translations — href/src schemes are narrow and attack-specific, and no legitimate translation needs `javascript:` or `data:`. The fix therefore blocks these schemes outright without changing other behaviour. ### Also fixed in 4.0.8 - **`debug` / `saveMissing` URL-parameter substring match.** The previous detection `window.location.search.indexOf('debug=true') > -1` matched the substring anywhere in the query string. A URL like `?nosaveMissing=true` silently enabled `saveMissing` mode, causing the victim's browser to POST every unknown translation key to the configured `addPath` — a form of CSRF-style abuse of missing-key reporting. `?track_debug=true` enabled verbose debug logging, leaking i18next internals to the console. Now uses `URLSearchParams` for exact parameter matching. - **Optional `sanitize(html, ctx)` hook.** The library's core purpose is to render HTML from translations — a behaviour that is safe only when the translation source is fully trusted. Applications with partially-trusted sources (user-contributed locales, third-party CDN, MITM-exposed HTTP backend) can now wire a sanitizer (e.g. DOMPurify) via `i18next.options.sanitize`. Defaults to pass-through to preserve existing behaviour for the main use case. ### Affected versions All versions of `i18nextify` prior to **4.0.8**. ### Patch Fixed in **4.0.8**. The URL-scheme blocklist is `^\s*(javascript|data|vbscript|file)\s*:` (case-insensitive) applied to each translated value before it is joined back into the `href`/`src` attribute. Values matching the blocklist are replaced with an empty string so the attribute becomes harmless rather than leaving the attacker's URL in place. ### Workarounds No workaround short of upgrading. If you cannot upgrade immediately, audit every translation file for `javascript:`, `data:`, `vbscript:`, and `file:` prefixes in any value that may reach an `href`/`src` position, and restrict translation-file write access to trusted operators. Serving translations over HTTPS and pinning the translation backend to an internal origin reduce the MITM surface. ### Credits Discovered via an internal security audit of the i18next ecosystem.

Source published

22 Apr 2026 17:42:24 UTC

Source modified

11 May 2026 13:53:13 UTC

Observed here

24 Oct 2026 13:17:17 UTC

Source terms

GitHub Advisory Database · CC-BY-4.0

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This view projects the publisher's source fields for reading; the original JSON retains additional fields and CVE enrichment containers. Attribution: osv · GitHub Advisory Database · CC-BY-4.0. Source text is retained; field grouping and change labels are provided by ChangeIntel.

CVSS_V3 · CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:C/C:L/I:L/A:N

Publisher rating · MODERATE