security

A write tool that asks before it writes needs three things the MCP SDK does not give you: an approval bound to the exact diff, a precondition on the file it previewed, and an integrity-protected requestState. Verified end to end on @modelcontextprotocol/server 2.0.0 against protocol revision 2026-07-28, including the argument-swap that gets past a naive confirm.

GitHub's August 6, 2026 changelog adds allowedMcpServers and deniedMcpServers to copilot/managed-settings.json. URL and argv matchers, deny-wins precedence, and a fail-closed default the older name-based registry never had.

Manual gates every tool call on you. Auto mode gates them on a classifier with 32 built-in block rules. The mode that surprises people is neither: acceptEdits auto-approves rm, mv, and sed, not just file edits. Measured on Claude Code 2.1.123.

NuGet.org drops the 365-day API key option on August 17, 2026, caps new keys at 30 days, and expires every key created before that date on November 1. Here is what breaks and how to move a publish workflow to OIDC trusted publishing.

Claude Code only consults Edit(path) and Read(path) rules. A Write(src/**) allow or deny rule is accepted and then silently ignored. Use Edit() instead.

Claude Code, Cursor, and the GitHub Copilot coding agent all ship host allowlists for outbound traffic, and all three default to something looser than you want. The exact settings keys, a policy you can copy, and the four surfaces the allowlist does not cover.

Preview 6 rejects unsafe cross-origin browser requests by default, reading the Sec-Fetch-Site header instead of an antiforgery token. Here is what it blocks and how to opt out.

Cato AI Labs disclosed CVE-2026-50548 and CVE-2026-50549, a pair of 9.8 CVSS flaws in Cursor's terminal sandbox. A poisoned MCP response or web result can escape the sandbox and run code. Cursor 3.0 is the fix.

A complete, working setup for JWT bearer authentication in an ASP.NET Core 11 minimal API: install the package, wire up AddAuthentication().AddJwtBearer(), issue a token, protect endpoints with RequireAuthorization, add role and claim policies, and test the whole thing with dotnet user-jwts.

Use cookie authentication for any app where the browser is the only client, and reserve JWT bearer tokens for APIs called by mobile apps, other services, or third parties. Here is the full decision matrix.