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VulnerabilityPublished

CVE-2026-10032: Google @a2ui/web_core · Cross-site Scripting

Affects Google @a2ui/web_coreSource CVE Database V5

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Not known to be exploited · CVSS 6.1 Medium.

Data as of 2 Nov 2026, 22:58 UTC

CVSS 4.0 base score
6.1Medium
How severe the flaw is on the 0–10 CVSS scale.
EPSS
0.1% chance of exploitation in 30 days – higher than 2% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:P/VC:H/VI:H/VA:L/SC:N/SI:N/SA:N/E:U

Exploitation evidence

  1. Disclosed: evidence found.

    CVE published 4 Aug 2026

  2. Detectable: no evidence on record.

    No public nuclei template indexed

  3. Weaponized: no evidence on record.

    No public exploit code indexed in Metasploit or Exploit-DB

  4. Exploited in the wild: no evidence on record.

    Not in CISA KEV and no source reports exploitation

  5. Observed by OffSeq Mirage: no evidence on record.

    No attack traffic recorded by OffSeq Mirage sensors

A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 2 Nov 2026.

What to do

Affected software

ProductAffectedFixed in
Google@a2ui/web_coreAffected
  • 0.9.0 – 0.10.1
11 affected builds
Fixed in–
npm@a2ui/web_corepkg:npm/@a2ui/web_coreOther threatsAffected
  • 0.9.0 – 0.10.1
11 affected builds
Fixed in–

Check your own hosts for these packages with threat-finder (opens in a new tab), our free open-source scanner.

AI-suggested

Until a fix is available, users should avoid using affected versions or implement additional input validation and sanitization on URLs passed to window.open(). Consider disabling or restricting the use of the Button component's functionCall action with user-controlled URLs if feasible.

Description

### Summary The `openUrl` function in `@a2ui/web_core` passes an agent-controlled URL directly to `window.open()` without validating the URI scheme. A malicious agent can supply a `javascript:` URI as the `url` argument of a `Button` component's `functionCall` action. When the user clicks the rendered button, arbitrary JavaScript executes in the victim application's browser origin, constituting a stored/reflected XSS. No non-default configuration is required; the Basic Catalog is enabled by default. ### Details The vulnerability exists in the `openUrl` function implementation within the Basic Catalog of `@a2ui/web_core` (commit `23a003248abbf59da6c376ea64ace91d82d209ff`). **Sink** — `renderers/web_core/src/v0_9/basic_catalog/functions/basic_functions.ts:428-430`: ```ts export const OpenUrlImplementation = createFunctionImplementation(OpenUrlApi, args => { if (args.url && typeof window !== 'undefined' && window.open) { window.open(args.url, '_blank'); } }); ``` `window.open` is called unconditionally with the agent-supplied `args.url` value. No scheme allowlist or blocklist is applied. **Insufficient schema validation** — `renderers/web_core/src/v0_9/basic_catalog/functions/basic_functions_api.ts:453-458`: ```ts export const OpenUrlApi = { name: 'openUrl' as const, returnType: 'void' as const, schema: z.object({ url: z.preprocess(v => (v === undefined ? undefined : String(v)), z.string()), }), }; ``` The Zod schema only requires a `string`; `javascript:` URIs pass validation without any rejection. **Full source-to-sink data flow:** 1. `renderers/web_core/src/v0_9/basic_catalog/components/basic_components.ts:356` — `ButtonApi` accepts `action: ActionSchema` (entry point). 2. `renderers/web_core/src/v0_9/schema/common-types.ts:126-130` — `ActionSchema` permits `{ functionCall: FunctionCallSchema }`. 3. `renderers/web_core/src/v0_9/rendering/generic-binder.ts:243-255` — on click, bound action calls `resolveDeepSync` then `dispatchAction`. 4. `renderers/web_core/src/v0_9/rendering/data-context.ts:93-105` — `resolveDynamicValue` detects the `call` key and invokes the named function. 5. `renderers/web_core/src/v0_9/catalog/types.ts:177-186` — catalog invoker runs `fn.schema.parse(rawArgs)` then `fn.execute()`. 6. `renderers/web_core/src/v0_9/basic_catalog/functions/basic_functions_api.ts:453-458` — `OpenUrlApi` validates `url` as `z.string()` only (no scheme check). 7. `renderers/web_core/src/v0_9/basic_catalog/functions/basic_functions.ts:428-430` — **sink**: `window.open(args.url, '_blank')` executes the `javascript:` URI. **All three renderers implemented in the A2UI repository are affected:** - React: `renderers/react/src/v0_9/catalog/basic/components/Button.tsx:33` — `onClick={props.action}` - Lit: `renderers/lit/src/v0_9/catalogs/basic/components/Button.ts:112` — `@click=${() => props.action()}` - Angular: `renderers/angular/src/v0_9/catalog/basic/button.component.ts:103-110` — `handleClick()` → `dataContext.resolveAction` → `dispatchAction` Any other A2UI renderer which depends on `web_core` and uses its basic catalog implementation is also affected. ### Remediation The issue was fixed in [https://github.com/a2ui-project/a2ui/pull/1707](https://github.com/a2ui-project/a2ui/pull/1707) and released in web\_core version 0.10.2, by blocking URLs that do not use the HTTP or HTTPS schemes, or those that are invalid. Please fix this issue in your project by depending on a @a2ui/web\_core version equal or greater than 0.10.2.

References

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