{"id":"GHSA-w937-fg2h-xhq2","summary":"locize Client SDK: Cross-origin DOM XSS & Handler Hijack Through Missing e.origin Validation in InContext Editor ","details":"### Summary\n\nVersions of the `locize` client SDK (the browser module that wires up the locize InContext translation editor) prior to 4.0.21 register a `window.addEventListener(\"message\", …)` handler that dispatches to registered internal handlers (`editKey`, `commitKey`, `commitKeys`, `isLocizeEnabled`, `requestInitialize`, …) **without validating `event.origin`**.\n\nThe pre-patch listener in `src/api/postMessage.js` gates dispatch on `event.data.sender === \"i18next-editor-frame\"` — that value sits inside the attacker-controlled message payload, not the browser-enforced origin. Any web page that could embed or be embedded by a locize-enabled host — an iframe on a third-party page, a `window.open`-ed victim, a parent frame reaching down — could send a crafted `postMessage` and trigger the internal handlers.\n\n### Impact\n\nDepending on which handler the attacker invokes, distinct consequences follow. All of them share the same root cause: the handlers implicitly assumed the payload came from the real editor iframe.\n\n- **Cross-origin DOM XSS** via `editKey` / `commitKeys`: the pre-patch `handleEditKey` assigned attacker-controlled payload values to `item.node.innerHTML` and to `item.node.setAttribute(attr, value)`. That allowed planting `\u003cscript\u003e`, `\u003cimg onerror\u003e`, or `onclick`/`onload`/`onfocus` event handlers; and on attribute writes, `href=\"javascript:…\"` / `src=\"data:text/html,\u003cscript\u003e…\"` / `style=\"…\"` / etc.\n\n- **`api.source` / `api.origin` hijack** via `isLocizeEnabled`: the handler set `api.source = e.source; api.origin = e.origin` — attacker-controlled values. All subsequent `sendMessage` calls (which post translations, callbacks, etc., back toward `api.source`) would go to the attacker window rather than the real editor, leaking translation content and any metadata the SDK forwards.\n\n- **CSS-injection / layout-escape** via `requestPopupChanges`: `containerStyle.height` / `.width` were interpolated into `calc()` expressions and `popup.style.setProperty()` without validation, allowing attackers to inject additional CSS declarations (semicolons, `behavior:url()` on legacy IE, CSS-exfil patterns) into the popup inline style.\n\nExploitation requires the attacker-owned page to share a window reference with the locize-enabled host: typical vectors are an `iframe` on an attacker-controlled page, a `window.opener`/`window.open` relationship, or a parent frame that can `postMessage` into an embedded locize host. The SDK intended model is that only the editor iframe at `https://incontext.locize.app` (or the configured staging/development origin) can reach these handlers.\n\n### Affected versions\n\nAll versions of `locize` prior to **4.0.21**.\n\n### Patch\n\nFixed in **4.0.21**. Two layers:\n\n1. **Primary** — validate `event.origin` at the top of `window.addEventListener(\"message\", …)` in `src/api/postMessage.js`. The expected origin is the configured iframe origin (`getIframeUrl()`), so custom environments continue to work. Messages from any other origin are silently dropped before any handler runs.\n\n2. **Defence-in-depth** — `handleEditKey` now rejects dangerous attribute-name writes (`on*`, `style`) and `javascript:` / `data:` / `vbscript:` / `file:` URLs on `href` / `src` / `action` / `formaction` / `xlink:href`; `innerHTML` assignments are sanitised through a throwaway DOMParser document (stripping `\u003cscript\u003e`, `\u003ciframe\u003e`, `\u003cobject\u003e`, `\u003cembed\u003e`, `\u003clink\u003e`, `\u003cmeta\u003e`, `\u003cbase\u003e`, `\u003cstyle\u003e` plus event handlers and dangerous URL schemes). Legitimate translation formatting (`\u003cb\u003e`, `\u003cem\u003e`, `\u003cstrong\u003e`, `\u003ca href=\"https://…\"\u003e`, etc.) passes through.\n\n3. **CSS-injection** — `handleRequestPopupChanges` now requires `containerStyle.height` / `.width` to match a strict CSS length pattern; malformed values are dropped silently.\n\n### Workarounds\n\nNo workaround short of upgrading.\n\n### Credits\n\nDiscovered via an internal security audit of the locize ecosystem.","aliases":["CVE-2026-41886"],"modified":"2026-05-13T13:54:34.252474Z","published":"2026-04-22T20:32:11Z","database_specific":{"github_reviewed_at":"2026-04-22T20:32:11Z","nvd_published_at":"2026-05-08T16:16:12Z","cwe_ids":["CWE-346","CWE-79"],"severity":"HIGH","github_reviewed":true},"references":[{"type":"WEB","url":"https://github.com/locize/locize/security/advisories/GHSA-w937-fg2h-xhq2"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-41886"},{"type":"WEB","url":"https://github.com/locize/locize/commit/d006b75fadb8e8ab77b023e462850fc6e9170735"},{"type":"WEB","url":"https://developer.mozilla.org/en-US/docs/Web/API/Window/postMessage#security_concerns"},{"type":"PACKAGE","url":"https://github.com/locize/locize"},{"type":"WEB","url":"https://github.com/locize/locize/releases/tag/v4.0.21"}],"affected":[{"package":{"name":"locize","ecosystem":"npm","purl":"pkg:npm/locize"},"ranges":[{"type":"SEMVER","events":[{"introduced":"0"},{"fixed":"4.0.21"}]}],"database_specific":{"source":"https://github.com/github/advisory-database/blob/main/advisories/github-reviewed/2026/04/GHSA-w937-fg2h-xhq2/GHSA-w937-fg2h-xhq2.json"}}],"schema_version":"1.9.0","severity":[{"type":"CVSS_V3","score":"CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:C/C:L/I:H/A:L"}]}