On October 14, 2026, Noma Labs published its account of SneakPeek, a flaw it reported in Claude Code Desktop’s HTML preview pane. Noma said Anthropic’s final fix shipped on August 17 in Claude Desktop 1.30096.1 and later. Noma’s disclosure traces how a Web Worker bypassed an earlier patch before the broader fix.
What SneakPeek affected
Noma reported that the issue was in Claude Code Desktop’s automated HTML preview pane. Its proof of concept involved a developer cloning a repository and asking Claude Code Desktop to edit a coverage report. When the preview rendered the HTML file, its JavaScript could run without a separate approval for the preview script, according to Noma.
The code ran in the preview renderer—not as an action by Claude’s AI agent. Noma’s account describes a possible route for that code to read local files and send data to a remote server.
Why the file-size threshold mattered
Noma described two rendering paths. HTML files under 256 KB used data: URLs and a Content Security Policy (CSP), a browser security rule that blocked script execution. Files over 256 KB were written to a temporary file and loaded through file://. Noma said that path lacked the CSP coverage and that a request filter was inactive when static HTML files were rendered directly from disk.
The proof of concept used the larger-file path to access local data. Noma named potential targets including AWS credentials, GitHub and npm tokens, SSH private keys, Kubernetes credentials, Docker registry authentication, and Claude OAuth tokens.
How the first patch was bypassed
Noma said Anthropic issued an initial patch on July 24, 2026, that blocked direct file reads from the preview’s main page context. Noma reported the same day that moving the file-reading code into a Web Worker created from a blob: URL bypassed that patch: the worker ran in a context the patch did not cover. On August 3, Noma said Anthropic confirmed the first fix was incomplete. The later fix addressed the reported issue, according to Noma.
Noma’s disclosure gives this chronology:
| Date | Event Noma reported |
| July 4, 2026 | Noma reported SneakPeek to Anthropic with a proof of concept. |
| July 9, 2026 | Anthropic triaged the report and assigned CVSS v4.0 8.7 (High), according to Noma. |
| July 24, 2026 | Anthropic issued an initial patch; Noma reported the Web Worker bypass. |
| August 3, 2026 | Noma said Anthropic confirmed the first fix was incomplete. |
| August 17, 2026 | Noma said the final fix shipped through auto-update in Claude Desktop 1.30096.1 and later. |
Noma described the demonstration as a proof of concept; its disclosure does not report exploitation against real users.
