diff --git a/server/routes.test.ts b/server/routes.test.ts
new file mode 100644
index 0000000..91c6af3
--- /dev/null
+++ b/server/routes.test.ts
@@ -0,0 +1,33 @@
+import { describe, it, expect } from "vitest";
+import crypto from "crypto";
+
+// Helper function mirroring webhook signature logic in server/routes.ts
+function computeWebhookSignature(data: any, customSecret?: string): string {
+  const hmacSecret = customSecret || process.env.IDSEC_HMAC_SECRET || "idsec_secret_salt";
+  const payloadString = JSON.stringify(data);
+  return crypto.createHmac("sha256", hmacSecret).update(payloadString).digest("hex");
+}
+
+describe("Webhook HMAC signature calculation", () => {
+  it("should calculate signature using IDSEC_HMAC_SECRET when set", () => {
+    const data = { event: "webhook.test", id: 1 };
+    const secret = "super_secret_env_key";
+
+    process.env.IDSEC_HMAC_SECRET = secret;
+    const signature = computeWebhookSignature(data);
+    const expected = crypto.createHmac("sha256", secret).update(JSON.stringify(data)).digest("hex");
+
+    expect(signature).toBe(expected);
+    delete process.env.IDSEC_HMAC_SECRET;
+  });
+
+  it("should fallback to default salt when IDSEC_HMAC_SECRET is unset", () => {
+    delete process.env.IDSEC_HMAC_SECRET;
+    const data = { event: "webhook.test", id: 1 };
+
+    const signature = computeWebhookSignature(data);
+    const expected = crypto.createHmac("sha256", "idsec_secret_salt").update(JSON.stringify(data)).digest("hex");
+
+    expect(signature).toBe(expected);
+  });
+});
diff --git a/server/routes.ts b/server/routes.ts
index d10cf6b..2876b70 100644
--- a/server/routes.ts
+++ b/server/routes.ts
@@ -2450,10 +2450,12 @@ CSAF: ${baseUrl}/.well-known/csaf/provider-metadata.json
         return res.status(400).json({ message: "Missing required fields" });
       }
       
-      // Create webhook payload with cryptographic signature
+      // SECURITY: Avoid hardcoding cryptographic HMAC secret salts in source code.
+      // Load secret from environment variable IDSEC_HMAC_SECRET with a fallback for local development.
+      const hmacSecret = process.env.IDSEC_HMAC_SECRET || "idsec_secret_salt";
       const payloadId = uuidv4();
       const payloadString = JSON.stringify(data);
-      const signature = crypto.createHmac("sha256", "idsec_secret_salt").update(payloadString).digest("hex");
+      const signature = crypto.createHmac("sha256", hmacSecret).update(payloadString).digest("hex");
       
       const payload = {
         id: payloadId,