Grok Build's share links left 35,000 apps open to anyone, including SpaceXSI's own

Grok Build, the AI app builder from SpaceXSI (the company formed when SpaceX and xAI merged), has been exposing the data inside thousands of apps its users made, according to research from security firm Claroc first reported by Ars Technica. Among the exposed projects were two dozen apps built by SpaceXSI's own staff.

How the leak worked

Grok Build lets you describe an app in plain language and get a working version within minutes. To show it to coworkers, you share a link. Those links are meant to be unguessable: each one starts with a few randomly chosen words, a common approach in which simply holding the URL acts as the key.

The problem is where the randomness sits. In Grok Build's links, the random words form the subdomain, the part in front of grok.me. Whenever a browser looks up a subdomain that's never been seen before, that lookup can be captured by passive DNS services, which keep searchable records of them. So the "secret" part of each link ends up in a public index. Google Docs and similar services avoid this by putting the random token in the path after the domain name, which DNS lookups never see.

Claroc said a passive DNS search returned 43,601 links ending in grok.me. More than 35,000 of them, close to 95%, opened the app and everything stored in it for whoever clicked.

What was exposed

According to Ars, the open apps held internal business plans, advertising proposals, medical exam results, employee names and ID numbers, and operational checklists from a cruise line. Some belonged to people working at Fortune 500 companies and at a defense contractor.

Claroc also found 24 apps built by SpaceXSI, including a confidential onboarding plan for a new enterprise sales hire and a sales territory map covering 594 accounts. Claroc says it alerted SpaceXSI on Sunday and, after getting no reply, flagged the problem publicly on X. The 24 SpaceXSI apps were pulled within hours of Ars asking the company about them, but most of the other exposed apps were still reachable when Ars published.

A dispute over the default

A representative for Cursor, the AI coding company SpaceXSI recently acquired, told Ars that Grok Build apps are private by default and only go public if their creator chooses to share them. Claroc's own tests found the opposite: the sharing setting defaulted to "Anyone with the link," and users had to change it to "invited users" or "only you" themselves.

Grok Build isn't the only tool that gives each app its own web address. Claroc noted that Lovable, Bolt and Replit do the same, so the same DNS trail exists for their apps too, though Grok Build is where it found by far the most exposed data.

Why it matters

"Vibe coding" tools have made it easy for people who aren't developers to build internal software in an afternoon, and a lot of that software ends up holding real company data. This case shows how one small design choice, where a random string sits in a URL, can turn a convenience feature into a public directory of private apps. It isn't a one-off, either: Ars notes that Meta recently suspended a link-sharing feature in its Muse agent after it was also found leaking sensitive data. Expect security teams to start asking which AI app builders their employees use, and how those apps are shared.