TL;DR
Security researchers cited in a June 2026 ThorstenMeyerAI report described three Claude Code-related attack paths involving local configuration, MCP traffic and repository hooks. Anthropic patched the Check Point-reported CVEs, while Mitiga Labs’ npm-based token-theft chain was described as live and outside Anthropic’s patch scope.
Security research cited in a June 2026 ThorstenMeyerAI report says three disclosed Claude Code-related flaws exposed developers to token theft, API-key exfiltration and code execution risks, putting new attention on coding agents as a security surface for teams connecting them to GitHub, Jira, Confluence and internal services.
The report cites Mitiga Labs, Check Point Research, SecurityWeek, all-about-security, Computerwoche commentary by cybersecurity engineer Anjali Gopinadhan Nair and Anthropic documentation. It describes a shared pattern: local files and integrations that developers may treat as configuration can also affect how an agent routes traffic, runs hooks and accesses external systems.
According to the report, Check Point Research disclosed CVE-2025-59536, described as remote code execution through repository hooks, and CVE-2026-21852, described as API-key exfiltration. Those issues were reported as patched after disclosure to Anthropic.
Mitiga Labs separately described a supply-chain attack path in which a malicious npm package rewrites ~/.claude.json, redirects authenticated MCP traffic and captures long-lived OAuth tokens for connected services. The ThorstenMeyerAI report says that path remained live at publication and was treated by Anthropic as outside patch scope. Anthropic’s full reasoning is not provided in the source material.
Your Coding Agent Is an Attack Surface
● SecurityThree disclosed flaws turned Claude Code’s local config and MCP integrations into silent paths for token theft and code execution. Some fixes are yours to make — and the lesson applies to every agentic dev tool, not one.
The config files most teams treat as passive metadata are, in practice, active execution paths.
~/.claude.json, reroutes MCP traffic, and intercepts long-lived OAuth tokens for GitHub, Jira, Confluence.How the unpatched Mitiga path works — at the level its researchers published. (Defensive overview, no exploit detail.)
~/.claude.json.For teams running Claude Code — or any coding agent — in production.
~/.claude.json/permissions; disconnect what you don’t use.Anthropic patched the Check Point CVEs fast — responsible disclosure worked. The npm post-install hook is an industry-wide supply-chain risk class, not Anthropic’s invention.
Anthropic calls the Mitiga chain “out of scope.” But consenting to install a package isn’t consenting to having your SaaS credentials intercepted — and plaintext tokens in the router file turn a generic risk into a specific one.
Independent commentary, produced with AI assistance under human editorial oversight; the views are the author’s own and may change. This is security analysis and opinion, not professional security, legal, or financial advice; verify specifics against vendor advisories and the primary research before acting. It describes publicly disclosed vulnerabilities at the level reported by their researchers and is for defensive purposes only — no exploit code or attack instructions. Sources: Computerwoche (Anjali Gopinadhan Nair), Mitiga Labs, Check Point Research, SecurityWeek, all-about-security, and Anthropic’s documentation, read as of June 2026. References to companies, researchers, and CVEs are factual and analytical and imply no affiliation or endorsement.
Agent Tokens Expand Exposure
The issue matters because coding agents often sit closer to sensitive systems than a browser session. A developer may connect an agent to source code, issue trackers, cloud tooling, internal APIs and production-adjacent credentials. If an attacker captures an agent’s tokens or changes where the agent sends traffic, the reach can extend across several work systems.
The report argues that agent configuration should be treated as active security-sensitive code, not passive metadata. That interpretation is based on the described behavior of Claude Code local config, MCP endpoints, repository hooks and environment-linked credentials.
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Three Disclosures, One Pattern
The June 2026 report groups the findings into three strands. Mitiga Labs focused on silent token theft through npm install behavior and Claude Code configuration. Check Point Research focused on code execution and API-key exposure tied to repository behavior. SecurityWeek and all-about-security were cited on a source leak that later fed fake GitHub repositories pushing malware through social engineering.
The report credits Anthropic with patching the Check Point-reported CVEs quickly after responsible disclosure. It also frames the npm post-install hook issue as a wider software supply-chain risk, not a risk invented by Anthropic or limited to Claude Code.
“The config files most teams treat as passive metadata are, in practice, active execution paths.”
— ThorstenMeyerAI report
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Unresolved Mitiga Attack Path
It is not yet clear from the provided source whether Anthropic plans any product change for the Mitiga-described chain. The report says Anthropic treated it as out of scope, but does not include a direct Anthropic statement explaining that position.
The scope of real-world exploitation is also unclear. The source material describes the chain as live and technically possible, but does not confirm how many developers or organizations were affected.
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Teams Review Agent Config
The immediate next step for teams using Claude Code is to update patched versions, audit ~/.claude.json, review MCP endpoints and proxy settings, restrict OAuth scopes and remove unused service connections. The report also recommends reviewing npm post-install behavior, cleaning affected hosts before rotating tokens, and isolating coding-agent sessions from production secrets.
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Key Questions
What was the actual development?
A June 2026 report compiled multiple security disclosures showing that Claude Code’s local configuration, MCP integrations and repository behavior can become paths for token theft, API-key exposure or code execution.
Were the Claude Code vulnerabilities patched?
The Check Point-reported CVEs were described as patched by Anthropic. The Mitiga-described npm and config-based token-theft path was described as live and outside Anthropic’s patch scope.
Why does MCP matter in this story?
MCP connections can link a coding agent to external services. If traffic is redirected or tokens are exposed, an attacker may gain access to connected systems rather than just a single local session.
What should developers check first?
Developers should update Claude Code, inspect ~/.claude.json for unfamiliar endpoints or proxy settings, review npm install hooks, narrow service permissions and rotate tokens after removing any malicious local changes.
Source: Thorsten Meyer AI
