Add security threat model and wire AGENTS.md -> SECURITY.md -> THREAT_MODEL.md

AGENTS.md

@@ -558,3 +558,16 @@ Key conventions:
 - **Testing**: JUnit 5 (Jupiter) + Mockito (Java; a small number of legacy JUnit 4 tests still exist), Playwright (frontend E2E)
 - **Logging**: SLF4J + Log4j2
 - **License**: Apache License 2.0 — all new files need the ASF header
+
+## Security
+
+Security model: [SECURITY.md](./SECURITY.md), which links to the project's
+threat model at [THREAT_MODEL.md](./THREAT_MODEL.md).
+
+Agents that scan this repository should consult `THREAT_MODEL.md` for the
+project's in-scope / out-of-scope declarations, the security properties it
+provides and disclaims, the configuration knobs whose defaults change the
+security envelope, and the known non-findings (recurring false positives)
+before reporting issues. In particular, Apache Zeppelin executes user-supplied
+notebook code through its interpreters by design — that is the product's
+function, not a vulnerability; see `THREAT_MODEL.md` §3, §9, and §11a.

SECURITY.md

@@ -0,0 +1,44 @@
+<!--
+Licensed to the Apache Software Foundation (ASF) under one or more
+contributor license agreements.  See the NOTICE file distributed with
+this work for additional information regarding copyright ownership.
+The ASF licenses this file to you under the Apache License, Version 2.0
+(the "License"); you may not use this file except in compliance with
+the License.  You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+-->
+
+# Security Policy
+
+## Reporting a Vulnerability
+
+Please report suspected security vulnerabilities in Apache Zeppelin privately
+to the Apache Security Team at <security@apache.org>, following the ASF process
+at <https://www.apache.org/security/>. Do not open public GitHub issues or pull
+requests for security reports.
+
+## Threat Model
+
+Apache Zeppelin's security threat model — what is in and out of scope, the
+security properties the project provides and disclaims, the adversary model,
+the configuration knobs whose defaults change the security envelope, and how
+findings are triaged — is documented in [THREAT_MODEL.md](./THREAT_MODEL.md).
+
+Note that Apache Zeppelin executes user-supplied notebook code through its
+interpreters by design; that capability is the product's primary function, and
+the threat model is about *who may reach it and with what isolation*. See
+`THREAT_MODEL.md` §3, §9, and §11a.
+
+## Operational Security Setup
+
+Operator-facing security configuration — authentication via Apache Shiro,
+notebook authorization, interpreter user impersonation, and HTTPS / HTTP
+security headers — is documented on the project website:
+<https://zeppelin.apache.org/docs/latest/setup/security/>