---
title: SneakPeek: Claude Code Desktop preview pane (CVSS 8.7) let a poisoned HTML file exfiltrate host secrets | ctxsec
url: https://ctxsec.com/items/sneakpeek-claude-code-desktop
description: ""
status: "confirmed (researcher + vendor fix)"
published: 2026-10-14
---

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[← Context & Harness Attacks](/context) · [markdown](/items/sneakpeek-claude-code-desktop.md)

confirmed (researcher + vendor fix)

2026-10-14

### SneakPeek: Claude Code Desktop preview pane (CVSS 8.7) let a poisoned HTML file exfiltrate host secrets

Noma Labs (Eli Ainhorn) disclosed an exploit chain in Claude Code Desktop's HTML preview pane. Files over 256KB loaded as `file://` without the CSP applied to smaller `data:` previews, and the request filter did not engage for static renders, so embedded JavaScript could `fetch()` local paths (SSH keys, AWS creds, OAuth tokens) and exfiltrate via `navigator.sendBeacon`. Delivery: clone a public repo, ask Claude to "review" a padded coverage-report HTML; the preview renders automatically. Anthropic scored CVSS 8.7, shipped an initial filter, then closed a blob:/Web Worker bypass; fixed in Claude Desktop 1.30096.1+ (Aug 17) via auto-update. Classic harness risk: the agent renders untrusted UI on the developer's machine.

Sources: [Noma Labs SneakPeek](https://noma.security/noma-labs/sneakpeek-how-the-preview-pane-in-claude-code-desktop-can-exfiltrate-your-data) · [Noma / PR Newswire](https://www.prnewswire.com/news-releases/noma-labs-uncovers-critical-security-vulnerabilities-in-claude-code-desktop-app-cvss-8-7-302908539.html)