Developing
Claroc sells security products, has no evidence of misuse and did not name affected companies; Meta has not said when sharing returns.
In 60 seconds
- Muse put each shared chat's title into the subdomain of its share link, followed by a random ID, so passive-DNS services logged the hostnames when pages were opened.
- Claroc found more than 6,800 share hostnames with one query and says a minority held sensitive material, such as a loan application and a bank fraud alert.
- Claroc reported the issue to Meta's bug bounty on October 8 and says it got no reply; Meta said it has "paused this functionality while we review this report".
- Claroc says it has no evidence anyone misused the shares; the hostnames remain in passive-DNS history.
Impact Layer
- What changed
- A popular consumer AI agent has switched off its share feature after a privacy design flaw was reported.
- Why it matters
- Titles often contain sensitive details, and putting them in hostnames exposed them to DNS logs.
- Who is affected
- Muse users, security and privacy teams and anyone designing share links for AI chats.
- Martech stack area
- AI, Data
- Stack impact
- Check whether your own share or preview links expose titles or identifiers in URLs, hostnames or logs.
- Business impact
- Moderate Based on PPC Land's account of Claroc's research and Ars Technica's reporting. The source dates differ (October 18 post versus a "Monday" report) and the total number of shares, notification of affected users and the date sharing returns are not stated.
- Related technologies
- What to watch
- When sharing returns and whether titles are removed from hostnames.
Meta paused sharing for Muse, its personal AI agent, on October 20, 2026 after Ars Technica asked about research from security firm Claroc, according to PPC Land.
What happened
- Muse put each shared chat’s title into the subdomain of its share link (under cf.metaaiusercontent.com), followed by a random ID.
- Passive-DNS services logged those hostnames when pages were opened, so Claroc found more than 6,800 share hostnames with one query and opened a few hundred without logging in.
- Claroc says a minority held sensitive material, including a loan application, an internal revenue review, a bank fraud alert with a partial account number and a staff vacation calendar.
Timeline and response
Muse launched in the US on September 8. Claroc collected data on October 7-8 and reported the issue to Meta’s bug bounty on October 8; its CTO says he got no reply. Meta said it has “paused this functionality while we review this report”. Claroc rechecked 40 shares on October 20 and none loaded. It says: “We have no evidence that anyone has misused these shares.”
Not stated
The total number of shares created, whether existing shares are deleted or only unreachable, whether users will be notified, when sharing returns, and the identity of affected companies. Claroc sells security products.
Our read
Never put user content in hostnames. DNS logs keep what URLs reveal.
Sources
- PPC Land: Meta halts Muse share links after 6,800 turn up in public DNS records (opens in a new tab)
Source for the research, Meta's response and the open questions.