Disclosed weakness · no CVE recorded

SneakPeek: Claude Desktop preview exposes local files

Anthropic · Claude Desktop / Claude Code preview pane

First documented disclosure · Review checkpoint

Summary

Noma demonstrated local-file disclosure when the preview automatically rendered crafted HTML.

Severity and exploitation evidence

High · 8.7/10 · CVSS 4.0. Severity source.

Exploitation not established: The reviewed sources establish a disclosed weakness or researcher demonstration, not malicious exploitation in the wild.

Technical severity is not a measure of observed attacks or of risk to your deployment. Attempts, demonstrations, and successful compromise retain the qualifications in the source.

How the weakness works

The large-file rendering path combined missing script restrictions with local-file access; a worker bypass defeated an initial fix.

Conditions required

A user asks Claude to inspect attacker-controlled HTML in a repository.

Potential impact

Potential exposure of local credentials and other readable files.

Affected versions and configurations

Preview implementations before the fix; the source does not identify a first affected release.

Fix and mitigation status

Claude Desktop 1.30096.1 and later, according to Noma’s August 17 fix timeline.

Practical next steps

Update and verify the desktop build; isolate untrusted artifact rendering and review credentials if exposure is suspected.

Operating lesson

Security checks must cover every rendering path and execution context.

Evidence and limits

Noma reports a final successful retest. Its October report says CVE/advisory publication was pending; no CVE identity is invented.

Related incident and research records

Related records can include laboratory demonstrations; a relationship does not itself establish exploitation.

Sources