--- title: MCP Security Fundamentals Course | daily.dev description: A free video course from AI Security University walks through the OWASP MCP top 10 risk categories for securing the Model Context Protocol. It opens with a... canonical: https://daily.dev/posts/mcp-security-fundamentals-course-dk0gp3yc1 twitter:card: summary_large_image twitter:site: @dailydotdev og:type: website og:site_name: daily.dev og:title: MCP Security Fundamentals Course | daily.dev og:description: A free video course from AI Security University walks through the OWASP MCP top 10 risk categories for securing the Model Context Protocol. It opens with a... og:url: https://daily.dev/posts/mcp-security-fundamentals-course-dk0gp3yc1 og:image: https://api.daily.dev/og/posts/dK0gp3yc1.png og:image:alt: MCP Security Fundamentals Course og:image:width: 1200 og:image:height: 630 og:locale: en --- > ## Documentation Index > Fetch the complete documentation index at: https://daily.dev/llms.txt > Use this file to discover all available pages before exploring further. # MCP Security Fundamentals Course **[freeCodeCamp](https://daily.dev/sources/freecodecamp)** · 130 min read · 202 upvotes · 6 comments ## Summary A free video course from AI Security University walks through the OWASP MCP top 10 risk categories for securing the Model Context Protocol. It opens with a real breach where a community-built Postmark MCP's version 1.0.16 secretly BCC'd every sent email to an attacker's address. The course introduces Simon Willis's 'lethal trifecta' framework (private data, untrusted content, external communications) and covers real incidents including EchoLeak against Copilot, a Supabase MCP data leak, a GitHub MCP private repo exposure, a Replit agent wiping a production database, and a CVSS 9.4 remote code execution flaw in Anthropic's MCP Inspector tool with over 38,000 weekly npm downloads. ## Full article daily.dev links to this article rather than hosting it. Read it at the original source: ## Questions this post answers ### How did the malicious Postmark MCP server leak user emails? A community-built Postmark MCP server for sending email through Postmark's API was compromised in version 1.0.16 with a single added line of code that BCC'd every outgoing email to an attacker-controlled address, fan@gshop.comclub. Since the tool already had legitimate permission to send email, the leak looked like normal, authorized behavior and wasn't a traditional exploit like a buffer overflow or SQL injection. _Anyone vetting third-party MCP servers before installing one can follow coverage like this on daily.dev._ ### What is the lethal trifecta in AI agent security? The lethal trifecta, coined by researcher Simon Willison, describes three conditions that together make an AI agent unconditionally vulnerable to data exfiltration: access to private data, exposure to untrusted content it doesn't control, and the ability to communicate externally. Any one or two of these alone are harmless, but when an agent has all three, attackers don't need a bug, they just use the agent's normal behavior against it. _Developers designing agent permissions can track frameworks like this through daily.dev._ ### What was the CVE in Anthropic's MCP Inspector tool and how was it exploited? MCP Inspector, Anthropic's official debugging tool for MCP servers with over 38,000 weekly npm downloads, had a critical remote code execution flaw rated CVSS 9.4, disclosed by researchers at Oligo and Teneal in June 2025. The local tool ran with no authentication and accepted connections from any origin; visiting a malicious website while Inspector ran let the site use DNS rebinding to execute code on the developer's machine with zero clicks. _Teams relying on MCP developer tooling can follow disclosures like this via daily.dev._ ## Community discussion Top comments from developers on daily.dev. **@hardik15** · 9 upvotes > Anything "Security" will be a hot topic for atleast few weeks going forward based on recent incidents **@trevorsuna** · 7 upvotes > The lethal-trifecta framing is useful because it shows why prompt filtering alone is not enough. Private data, untrusted content, and external actions need separate enforcement boundaries: scoped credentials, explicit egress rules, human approval for mutations, and audit logs outside the agent process. **@swarnasharmin** · 4 upvotes > How do you mitigate supply-chain risks in community-built MCPs when hidden exfiltration channels like unauthorized BCC headers bypass static analysis? **@webkmsyed** · 4 upvotes > @freecodecamp Videos really helpful for programmers but in my case I love to learn through Documents. **@renis** · 3 upvotes > We need this info. All need this info. Great. ## Similar posts on daily.dev - [Guide to the OWASP MCP Top 10](https://daily.dev/posts/guide-to-the-owasp-mcp-top-10-crlkplzyp) · Nordic APIs · 1 upvotes · 0 comments - [The Ultimate Guide to MCP Security Vulnerabilities](https://daily.dev/posts/the-ultimate-guide-to-mcp-security-vulnerabilities-4uxwe9stx) · Security Boulevard · 0 upvotes · 0 comments - [A Proposed MCP Server Security Evaluation Framework](https://daily.dev/posts/a-proposed-mcp-server-security-evaluation-framework-73btp3tpe) · Liran Tal · 1 upvotes · 0 comments - [First Malicious MCP in the Wild: The Postmark Backdoor That's Stealing Your Emails](https://daily.dev/posts/first-malicious-mcp-in-the-wild-the-postmark-backdoor-that-s-stealing-your-emails-pkglv3v8a) · Tech Lead Digest · 2 upvotes · 0 comments - [MCP Security: Understanding Vulnerabilities in Model Context Protocol](https://daily.dev/posts/mcp-security-understanding-vulnerabilities-in-model-context-protocol-hcscknky1) · marmelab · 4 upvotes · 0 comments --- Tags: [#security](https://daily.dev/tags/security), [#ai-agents](https://daily.dev/tags/ai-agents), [#mcp](https://daily.dev/tags/mcp), [#prompt-injection](https://daily.dev/tags/prompt-injection) [View this post on daily.dev](https://daily.dev/posts/mcp-security-fundamentals-course-dk0gp3yc1) ```json {"@context":"https://schema.org","@graph":[{"@type":"Organization","@id":"https://daily.dev/#organization","name":"daily.dev","url":"https://daily.dev","logo":{"@type":"ImageObject","url":"https://daily.dev/apple-touch-icon.png","width":180,"height":180},"sameAs":["https://twitter.com/dailydotdev","https://github.com/dailydotdev","https://www.linkedin.com/company/daily-dev-ltd"]},{"@type":"WebSite","@id":"https://daily.dev/#website","url":"https://daily.dev","name":"daily.dev","publisher":{"@id":"https://daily.dev/#organization"},"potentialAction":{"@type":"SearchAction","target":{"@type":"EntryPoint","urlTemplate":"https://daily.dev/search?q={search_term_string}"},"query-input":"required name=search_term_string"}}]} {"@context":"https://schema.org","@type":"TechArticle","headline":"MCP Security Fundamentals Course","url":"https://daily.dev/posts/mcp-security-fundamentals-course-dk0gp3yc1","mainEntityOfPage":{"@type":"WebPage","@id":"https://daily.dev/posts/mcp-security-fundamentals-course-dk0gp3yc1"},"datePublished":"2026-10-22T12:12:44.144Z","dateModified":"2026-10-22T12:13:13.425Z","description":"A free video course from AI Security University walks through the OWASP MCP top 10 risk categories for securing the Model Context Protocol. 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All need this info. Great.","datePublished":"2026-10-24T21:09:59.320Z","url":"https://daily.dev/posts/dK0gp3yc1#c-k7Ca9UH7e","author":{"@type":"Person","name":"Renis","url":"https://daily.dev/renis","image":"https://lh3.googleusercontent.com/a-/AOh14GibUeLAAy830VlX3NrKw0ySJNoswHch55m79hYL7w=s100"},"interactionStatistic":{"@type":"InteractionCounter","interactionType":{"@type":"LikeAction"},"userInteractionCount":3}}]} {"@context":"https://schema.org","@type":"FAQPage","@id":"https://daily.dev/posts/mcp-security-fundamentals-course-dk0gp3yc1#faq","mainEntity":[{"@type":"Question","name":"How did the malicious Postmark MCP server leak user emails?","acceptedAnswer":{"@type":"Answer","text":"A community-built Postmark MCP server for sending email through Postmark's API was compromised in version 1.0.16 with a single added line of code that BCC'd every outgoing email to an attacker-controlled address, fan@gshop.comclub. 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