diff --git a/pages/api/file/downloadblob.js b/pages/api/file/downloadblob.js
index fe2ab520..9cbe11f4 100644
--- a/pages/api/file/downloadblob.js
+++ b/pages/api/file/downloadblob.js
@@ -16,6 +16,19 @@ ApiProxy.get(async (req, res) => {
     var blobName = req.query.blobname;
     var checkHash = req.query.hash;
 
+    if (
+        typeof containerName === "undefined" ||
+        containerName.length === 0 ||
+        typeof casefolderID === "undefined" ||
+        casefolderID.length === 0 ||
+        typeof blobName === "undefined" ||
+        blobName.length === 0 ||
+        typeof checkHash === "undefined" ||
+        checkHash.length === 0
+    ) {
+        return res.status(400).json();
+    }
+
     var checkquerypath =
         "/api/file/downloadblob?container=" +
         containerName +
@@ -24,6 +37,10 @@ ApiProxy.get(async (req, res) => {
         "&blobname=" +
         blobName.trim();
 
+    if (hashAPIPath(checkquerypath) != "&hash=" + checkHash) {
+        return res.status(400).json();
+    }
+
     if (hashAPIPath(checkquerypath) == "&hash=" + checkHash) {
         const bloblocation =
             casefolderID + (blobName.indexOf(".json") > 0 ? "/" : "/files/");
@@ -38,8 +55,6 @@ ApiProxy.get(async (req, res) => {
             "attachment; filename=" + decodeURI(blobName)
         );
         return res.status(200).send(downloaded);
-    } else {
-        return res.status(400).json();
     }
 });
 
diff --git a/pages/api/file/getawaitingsubmissionfromblobproxy.js b/pages/api/file/getawaitingsubmissionfromblobproxy.js
index f7f1b2f8..2e05852a 100644
--- a/pages/api/file/getawaitingsubmissionfromblobproxy.js
+++ b/pages/api/file/getawaitingsubmissionfromblobproxy.js
@@ -23,6 +23,11 @@ const BASE_URL = process.env.API_ROOT || `http://localhost:${port}`;
 export default async function ApiProxy(req, res) {
     var containerName = req.query.container;
     var checkHash = req.query.hash;
+
+    if (typeof containerName === "undefined" || containerName.length === 0) {
+        return res.status(400).json();
+    }
+
     var token = await getToken();
 
     var queryUrl =
diff --git a/pages/api/file/getbloblistproxy.js b/pages/api/file/getbloblistproxy.js
index 5e9f66e3..8032d1c8 100644
--- a/pages/api/file/getbloblistproxy.js
+++ b/pages/api/file/getbloblistproxy.js
@@ -24,6 +24,16 @@ export default async function ApiProxy(req, res) {
     var containerName = req.query.container;
     var casefolderID = req.query.casefolderID;
     var checkHash = req.query.hash;
+
+    if (
+        typeof containerName === "undefined" ||
+        containerName.length === 0 ||
+        typeof casefolderID === "undefined" ||
+        casefolderID.length === 0
+    ) {
+        return res.status(400).json();
+    }
+
     var token = await getToken();
 
     var queryUrl =
diff --git a/pages/api/file/getrepsblobproxy.js b/pages/api/file/getrepsblobproxy.js
index 0b199f1b..7b377b2d 100644
--- a/pages/api/file/getrepsblobproxy.js
+++ b/pages/api/file/getrepsblobproxy.js
@@ -23,6 +23,11 @@ const BASE_URL = process.env.API_ROOT || `http://localhost:${port}`;
 export default async function ApiProxy(req, res) {
     var containerName = req.query.container;
     var checkHash = req.query.hash;
+
+    if (typeof containerName === "undefined" || containerName.length === 0) {
+        return res.status(400).json();
+    }
+
     var token = await getToken();
 
     var queryUrl = "/api/file/getrepsblob?container=" + containerName;
diff --git a/tests/phase12/service-behaviour.test.cjs b/tests/phase12/service-behaviour.test.cjs
new file mode 100644
index 00000000..b906582a
--- /dev/null
+++ b/tests/phase12/service-behaviour.test.cjs
@@ -0,0 +1,169 @@
+const fs = require("fs");
+const path = require("path");
+const vm = require("vm");
+const assert = require("assert");
+
+const rootDir = path.resolve(__dirname, "..", "..");
+
+const loadModule = (relativePath, injected = {}) => {
+    const filePath = path.join(rootDir, relativePath);
+    let source = fs.readFileSync(filePath, "utf8");
+
+    source = source.replace(/import[\s\S]*?from\s+"[^"]+";\n?/g, "");
+    source = source.replace(
+        /export default async function\s+(\w+)\s*\(/,
+        "async function $1("
+    );
+    source = source.replace(/export const\s+/g, "const ");
+    source = source.replace(
+        /export default\s+(\w+);/g,
+        "module.exports.default = $1;"
+    );
+    source +=
+        '\nif (typeof ApiProxy !== "undefined" && !module.exports.default) module.exports.default = ApiProxy;\n';
+
+    const context = {
+        module: { exports: {} },
+        exports: {},
+        require,
+        process,
+        console: { log: () => {}, error: () => {} },
+        port: 3000,
+        ...injected
+    };
+
+    vm.runInNewContext(source, context, { filename: filePath });
+    return context.module.exports;
+};
+
+const createNextConnectMock = () => {
+    const router = {
+        handler: null,
+        use: () => {},
+        get(fn) {
+            this.handler = fn;
+        }
+    };
+    return () => router;
+};
+
+const createRes = () => {
+    const state = {
+        statusCode: null,
+        jsonBody: undefined,
+        sentBody: undefined,
+        headers: {}
+    };
+    return {
+        state,
+        status(code) {
+            state.statusCode = code;
+            return this;
+        },
+        json(payload) {
+            state.jsonBody = payload;
+            return payload;
+        },
+        send(payload) {
+            state.sentBody = payload;
+            return payload;
+        },
+        setHeader(name, value) {
+            state.headers[name] = value;
+        }
+    };
+};
+
+const tests = [];
+const test = (name, fn) => tests.push({ name, fn });
+
+test("downloadblob rejects missing hash with 400", async () => {
+    const calls = [];
+    const mod = loadModule("pages/api/file/downloadblob.js", {
+        hashAPIPath: () => "&hash=expected",
+        downloadFile: async (...args) => {
+            calls.push(args);
+            return Buffer.from("x");
+        },
+        nextConnect: createNextConnectMock(),
+        middleware: () => {}
+    });
+
+    const req = {
+        query: { container: "c1", casefolderID: "case-1", blobname: "f.pdf" }
+    };
+    const res = createRes();
+    await mod.default.handler(req, res);
+    assert.strictEqual(res.state.statusCode, 400);
+    assert.strictEqual(calls.length, 0);
+});
+
+test("downloadblob valid hash returns 200", async () => {
+    const mod = loadModule("pages/api/file/downloadblob.js", {
+        hashAPIPath: () => "&hash=expected",
+        downloadFile: async () => Buffer.from("file"),
+        nextConnect: createNextConnectMock(),
+        middleware: () => {}
+    });
+
+    const req = {
+        query: {
+            container: "c1",
+            casefolderID: "case-1",
+            blobname: "f.pdf",
+            hash: "expected"
+        }
+    };
+    const res = createRes();
+    await mod.default.handler(req, res);
+    assert.strictEqual(res.state.statusCode, 200);
+});
+
+test("getbloblistproxy rejects missing container with 400", async () => {
+    const mod = loadModule("pages/api/file/getbloblistproxy.js", {
+        getToken: async () => ({ access_token: "t" }),
+        hashAPIPath: () => "&hash=expected",
+        azureHeaders: () => ({}),
+        axios: { get: async () => ({ data: { ok: true } }) },
+        consoleLogger: () => {}
+    });
+
+    const req = { query: { casefolderID: "case-1" } };
+    const res = createRes();
+    await mod.default(req, res);
+    assert.strictEqual(res.state.statusCode, 400);
+});
+
+test("getawaitingsubmissionfromblobproxy rejects missing container with 400", async () => {
+    const mod = loadModule(
+        "pages/api/file/getawaitingsubmissionfromblobproxy.js",
+        {
+            getToken: async () => ({ access_token: "t" }),
+            hashAPIPath: () => "&hash=expected",
+            azureHeaders: () => ({}),
+            axios: { get: async () => ({ data: { ok: true } }) },
+            consoleLogger: () => {}
+        }
+    );
+
+    const req = { query: {} };
+    const res = createRes();
+    await mod.default(req, res);
+    assert.strictEqual(res.state.statusCode, 400);
+});
+
+const run = async () => {
+    let passed = 0;
+    for (const t of tests) {
+        await t.fn();
+        passed += 1;
+    }
+    console.log(
+        `Phase 12 behavioural tests passed (${passed}/${tests.length}).`
+    );
+};
+
+run().catch((error) => {
+    console.error(error);
+    process.exit(1);
+});