Anthropic’s Claude Code Desktop was exposed to an exploit chain dubbed “SneakPeek” in which a poisoned public repository could execute JavaScript in the app’s automatic HTML preview and quietly exfiltrate local credentials. Noma Security rated the chain CVSS 8.7 (High). Noma said Anthropic’s final security patch was verified and deployed on August 17, 2026, but users should still confirm their installed build and consult Anthropic’s current security advisory.
What the SneakPeek vulnerability did
SneakPeek targeted the preview pane in Claude Code Desktop. The pane is an Electron/Chromium rendering surface that displays HTML files Claude generates or edits. A public repository could include an attacker-controlled HTML file padded beyond 256 KB. When a developer asked Claude Code to review or modify that file, the preview rendered automatically. Its embedded script could then make outbound requests and transmit secrets readable by the local user account—without a click, confirmation dialog or other developer action.
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The attack therefore depended on a normal development task rather than an obviously suspicious executable. A repository could look like an ordinary project while its oversized HTML file turned the preview component into a credential-theft channel.
Why the preview was not safely isolated
Dark Reading, citing the disclosure by Noma Security, described three architectural gaps that combined to defeat the preview’s intended sandboxing:
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- No effective content security policy: the rendered document was not constrained by a policy that would have blocked or limited its script behavior.
- Unrestricted origin access: the page had access to web capabilities that should have been isolated from sensitive local application data.
- Inactive request filtering: network-request controls that could have stopped suspicious outbound traffic were not active.
Each weakness increased the danger of the others. Together they allowed JavaScript in a file presented as a preview to reach data and send it to an attacker-controlled destination.
What an attacker could steal
Reportedly reachable material included SSH private keys, AWS and other cloud credentials, GitHub credentials, API keys, Kubernetes configuration and Claude OAuth tokens. The risk is not limited to the contents of one file. Any secret readable by the developer’s local account could provide a route into source-control organizations, cloud resources, clusters or other development systems.
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| Potentially exposed material | Possible downstream consequence |
|---|---|
| SSH private keys | Unauthorized access to hosts or repositories where the key is trusted |
| AWS and other cloud credentials | Cloud-console or API access, resource changes and data theft |
| GitHub credentials | Repository access, code theft or malicious changes |
| API keys | Use of paid or privileged services under the victim’s account |
| Kubernetes configuration | Access to clusters and workloads governed by the configuration |
| Claude OAuth tokens | Unauthorized use of the associated account or integrations |
Whether a particular secret was exposed depends on what the local account could read and what the malicious script could reach. The published reports describe the categories of data at risk, not a guarantee that every installation contained or disclosed each item.
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Was SneakPeek patched?
Noma Security’s disclosure says the final security patch was verified and deployed on August 17, 2026, after collaborative work with Anthropic. The first fix was reportedly bypassed by the researchers who found the issue, leading to deeper architectural changes before the final remediation. Dark Reading and Noma publicly reported the exploit chain on October 14, 2026.
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Those dates describe the vendor’s reported remediation timeline, not the build installed on every computer. Check Claude Code Desktop’s About or update screen, compare the installed build with Anthropic’s current advisory, and apply the latest release through your organization’s approved software channel. Do not assume that an installation updated before August 17 includes the final fix, or that an unverified package is protected.
What to do if you opened a poisoned repository
Treat a suspected preview render as a possible credential exposure, even if you saw no warning and cannot find a changed file.
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- Stop using the affected workstation for privileged work. Disconnect it from sensitive development sessions and avoid entering new credentials until triage is complete.
- Record the repository and event. Preserve the repository URL or commit, the approximate time, the Claude Code Desktop build and any relevant application or network logs. Do not repeatedly reopen the project to reproduce the behavior.
- Rotate credentials from a clean device. Revoke and replace SSH keys, cloud access keys, source-control tokens, API keys, Kubernetes credentials and Claude OAuth tokens that the local account could read. Prefer short-lived credentials and least-privilege replacements.
- Review identity and cloud logs. Look for logins, API calls, token use, repository changes, new SSH sessions, unusual regions and unexpected outbound activity beginning around the preview event.
- Inspect source-control and cloud changes. Check for altered workflows, deploy keys, access policies, new users, modified cluster settings and other persistence mechanisms.
- Update or isolate the application. Install the vendor-confirmed patched build. If the build cannot be verified, remove the application from privileged workflows and ask your security team to examine the workstation.
- Scan for additional secrets. Use your organization’s endpoint monitoring and secret-scanning controls to find credentials stored in files, shell history, environment variables, editor settings and build artifacts.
Simply cloning a repository is not the same as triggering SneakPeek; the reported chain required Claude Code to process the malicious HTML and render it in the preview pane. However, logs may not make that distinction obvious, so an organization should investigate any machine on which the file was opened for review or editing.
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How teams can reduce the risk
Control automatic rendering
Restrict automatic previews of untrusted HTML in developer tools where policy allows. Treat generated documentation, demos and static-site files as executable content when they are opened inside an Electron or browser-based surface.
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Reduce the value of a workstation compromise
- Keep long-lived cloud keys, broad source-control tokens and production Kubernetes credentials off ordinary developer laptops.
- Use short-lived, device-bound or hardware-backed authentication where available.
- Separate personal development identities from production administration.
- Ensure endpoint detection can alert on unusual child processes, file access and outbound requests from developer applications.
Make revocation routine
Maintain an inventory of SSH keys, cloud identities, API tokens and OAuth grants so responders can revoke them quickly. Secret scanning should cover repositories, local configuration directories and build outputs, not only the latest commit.
Why this matters beyond Claude Code
SneakPeek demonstrates that a feature described as a preview can still be an execution surface. Electron and Chromium components inherit browser attack considerations, and a surrounding application’s sandbox is only as strong as its content policy, origin isolation and network controls. A routine code-review request can therefore become a supply-chain event when untrusted files are rendered automatically.
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