GHSA-9r75-g2cr-3h76 Vercel Workflow Allows Webhook Creation with Predictable User-Specified Tokens

• npm workflow: < 4.2.0-beta.64 → fixed in 4.2.0-beta.64 • npm @workflow/core: < 4.2.0-beta.64 → fixed in 4.2.0-beta.64

`createWebhook()` in Vercel Workflow DevKit accepts a user-specified `token` parameter that serves as the credential for the public webhook endpoint `/.well-known/workflow/v1/webhook/{token}`. Official documentation recommended predictable token patterns, making it possible for an unauthenticated remote attacker to guess the token and inject arbitrary payloads into the workflow execution context. Impact An attacker who guesses a webhook token can resume the associated workflow with an attacker-controlled HTTP request body, potentially triggering downstream side effects such as API calls, database writes, or deployments. Fix • Upgrade to version 4.2.0-beta.64. The fix removes the `token` option from `createWebhook()` so that webhook tokens are always randomly generated by the SDK. • Runs created with versions prior to 4.2.0-beta.64, that are 1) still active (i.e. running), and 2) have open hooks, are still susceptible to this vulnerability. If users suspect the hook tokens are predictable or leaked - consider cancelling those runs and restarting them on the latest patch. Workarounds In case a version upgrade is not possible, avoid passing predictable or guessable values to the `token` parameter of `createWebhook()`. Instead, users can either • switch from `createWebhook()` to `createHook()` instead and programmatically resume hooks using `resumeHook()` instead of the public webhook endpoint, or • use `createWebhook()` without passing a user-provided `token`, which uses a non-guessable random `nanoid` by default.