35,000 Grok Build apps are open to anyone with the link

A quick internal app built with Grok Build may be open to anyone who finds the link. Security firm Claroc tested 43,551 Grok Build app addresses on 10 November. Of the 37,571 still online, 35,578 opened all their data without a login. That is 94.7 percent.

Claroc published the findings on its own blog as the second post in its GhostShares series. The first post, in October, covered the same flaw on Meta's Muse chat sharing.

How the apps leaked

Grok Build is SpaceXSI's coding agent. A user types a prompt, and the service builds a running web app for them. Each app is given its own web address at a Grok subdomain.

A browser that visits the app does a DNS lookup on that subdomain. Passive DNS services record the lookup. That turns every app name into a public, searchable record. Claroc listed 43,551 of these addresses with standard tools.

The default access setting on every app is Anyone with the link. Claroc writes that this box is pre-selected when the app is published. The user has to change it to a private setting to keep the app from being open.

What was exposed

Claroc says it opened a sample of apps without signing in or sending any credentials. It found 24 apps built by SpaceXSI staff themselves. The documents included a confidential sales onboarding plan, a sales map covering 594 accounts, and eight ad proposals to U.S. federal clients. Two were brand safety playbooks for X.

Other apps belonged to third parties. Claroc names a hospital staff roster with 3,500 names. It names ICU patient lab results. It names a fire department rota. It names a cruise line crew list. It names a trucking recruiting list with 1,000 names and personal emails. It names a contractor timesheet with 18 passwords stored in plain text. Claroc says 30 organisations with more than 1,000 employees had data exposed. Six were Fortune 500 companies.

SpaceXSI's response

Claroc says it told SpaceXSI on Sunday. SpaceXSI took its own 24 apps offline. It then told Claroc that apps are private by default and that users must actively choose to share them. Claroc writes that the 24 SpaceXSI apps still open at the time of the scan contradict that claim.

SpaceXSI has not, in Claroc's account, contacted the third-party owners of the other 35,000 apps. Those apps were still public when Claroc published.

Audit your own apps today

Any team using Grok Build, or a similar builder such as Lovable, Replit, v0 or Bolt, carries the same risk. Three checks, from Claroc's own recommendations, take a few minutes each.

First, open every app you built in an incognito window with no login. Read what it serves to the visitor. If a page shows data, the app is public. Second, search passive DNS for your company's domain names and project words. A match tells you which apps anyone can find. Third, look at any files the app uses. A script file with an API key or a password inside is exposed when the app is.

The fix is a sign-in page that checks a user before the app answers with data. Claroc also asks SpaceXSI to change the default on new apps. The new default would be Only you, not Anyone with the link. Claroc also asks for a warning on apps that store data without a login. That warning does not exist yet.

Source

• GhostShares 2: Grok Apps Exposed xAI's Business Secrets and People's Private Data, Claroc.
• Ars Technica also covered the findings.