Replace "external" with "network" in CSP documentation

The term "external" is misleading for MCP Apps because developers
typically interpret it as "third-party." However, MCP App HTML runs in
a sandboxed iframe with no same-origin server, so *all* origins must be
declared—including where your own bundled JS/CSS is served from. Using
"network" instead avoids this confusion and aligns with the detailed
explanations in `patterns.md` and `spec.types.ts`.

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>
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Jonathan Hefner 2026-02-02 10:37:33 -06:00
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@ -201,7 +201,7 @@ See the [Display Modes](https://github.com/modelcontextprotocol/ext-apps/blob/ma
All Views run in sandboxed iframes with no access to the Host's DOM, cookies, or storage. Communication happens only through [`postMessage`](https://developer.mozilla.org/en-US/docs/Web/API/Window/postMessage), making it auditable.
Servers declare which external domains their UI needs via [CSP](https://developer.mozilla.org/en-US/docs/Web/HTTP/Guides/CSP) metadata. Hosts enforce these declarations — if no domains are declared, no external connections are allowed. This "restrictive by default" approach prevents data exfiltration to undeclared servers.
Servers declare which network domains their UI needs via [CSP](https://developer.mozilla.org/en-US/docs/Web/HTTP/Guides/CSP) metadata. Hosts enforce these declarations — if no domains are declared, no external connections are allowed. This "restrictive by default" approach prevents data exfiltration to undeclared servers.
See the [Security Implications](https://github.com/modelcontextprotocol/ext-apps/blob/main/specification/2026-01-26/apps.mdx#security-implications) section of the specification for the threat model and mitigations.