fix(security): remove allow-same-origin from MCP Apps sandbox iframes#1064
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zeroasterisk wants to merge 2 commits intogoogle:mainfrom
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fix(security): remove allow-same-origin from MCP Apps sandbox iframes#1064zeroasterisk wants to merge 2 commits intogoogle:mainfrom
zeroasterisk wants to merge 2 commits intogoogle:mainfrom
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This pull request restricts the sandbox permissions for MCP app iframes by removing several flags, including allow-same-origin, to improve security. Feedback suggests that while removing allow-same-origin is appropriate, other functional flags such as allow-forms, allow-popups, and allow-modals should be retained to ensure basic application features like form submissions and popups continue to work.
samples/client/lit/custom-components-example/ui/custom-components/mcp-apps-component.ts
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The Lit sample and shared sandbox proxy included allow-same-origin in iframe sandbox attributes, violating the MCP Apps guide/spec: - Lit outer iframe: removed sandbox attribute entirely (guide says don't sandbox the proxy iframe) - Lit sendSandboxResourceReady: allow-scripts only (was allow-scripts allow-forms allow-popups allow-modals allow-same-origin) - Shared sandbox.ts inner iframe default: allow-scripts only (was allow-scripts allow-same-origin allow-forms) The Angular sample already correctly used sandbox: 'allow-scripts'. Confirmed against MCP Apps spec (SEP-1865) and AppBridge SDK docs. Fixes security discrepancy found by Gemini Code Assist review on google#1062.
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Summary
Fixes a security discrepancy between the MCP Apps guide/spec and the Lit sample implementation. Found during review of PR #1062.
Problem
The Lit sample (
mcp-apps-component.ts) and shared sandbox proxy (sandbox.ts) includedallow-same-originin iframe sandbox attributes, violating:allow-same-origin"sandbox: "allow-scripts"onlyThe Angular sample (
mcp-app.ts) already correctly usedsandbox: 'allow-scripts'.Changes
mcp-apps-component.ts(outer iframe)sandbox="allow-scripts allow-forms allow-popups allow-modals allow-same-origin"mcp-apps-component.ts(sendSandboxResourceReady)sandbox: "allow-scripts allow-forms allow-popups allow-modals allow-same-origin"sandbox: "allow-scripts"sandbox.ts(inner iframe default)allow-scripts allow-same-origin allow-formsallow-scriptsMinimal change: 2 files, 1 commit.
Verification
sandbox: "allow-scripts"Related