diff --git a/addon/cleintsecret_check.py b/addon/cleintsecret_check.py
new file mode 100644
index 0000000..f48ed93
--- /dev/null
+++ b/addon/cleintsecret_check.py
@@ -0,0 +1,76 @@
+# clientsecret_check.py
+from mitmproxy import http
+from urllib.parse import urlparse, parse_qs
+from typing import List
+import lib.target as target
+from lib.report import save_report
+
+
+class ClientSecretChecker:
+    def is_oauth_uri(self, uri: str) -> bool:
+        qs = parse_qs(urlparse(uri).query)
+        keys = qs.keys()
+        return "client_id" in keys and ("client_secret" in keys or "client_secret" in uri)
+
+    def has_client_secret_in_uri(self, uri: str) -> bool:
+        qs = parse_qs(urlparse(uri).query)
+        return "client_secret" in qs
+
+    def is_post_with_client_secret(self, flow: http.HTTPFlow) -> bool:
+        if flow.request.method != "POST":
+            return False
+        content_type = flow.request.headers.get("Content-Type", "")
+        if "application/x-www-form-urlencoded" in content_type:
+            body = parse_qs(flow.request.get_text())
+            return "client_secret" in body
+        return False
+
+    def is_exposed_in_referer(self, flow: http.HTTPFlow) -> bool:
+        referer = flow.request.headers.get("Referer", "")
+        return "client_secret" in referer
+
+    def check_client_secret_leak(self, flow: http.HTTPFlow) -> List[str]:
+        messages = []
+
+        if self.has_client_secret_in_uri(flow.request.url):
+            messages.append("client_secret found in URL query string")
+
+        if self.is_post_with_client_secret(flow):
+            messages.append("client_secret found in POST body")
+
+        if self.is_exposed_in_referer(flow):
+            messages.append("client_secret exposed in Referer header")
+
+        return messages
+
+    def _report(self, flow: http.HTTPFlow, issues: List[str], direction: str):
+        desc = " | ".join(issues)
+        report_data = [{
+            'target': target.load(),
+            'status': "HIGH",
+            'title': f"OAuth Client Secret Exposure ({direction})",
+            'description': desc,
+            'uri': flow.request.url,
+        }]
+        save_report(report_data)
+        print(f"[INFO] Client Secret Leak Detected ({direction}): {desc}")
+
+    def request(self, flow: http.HTTPFlow) -> None:
+        try:
+            if not self.is_oauth_uri(flow.request.url):
+                return
+            issues = self.check_client_secret_leak(flow)
+            if issues:
+                self._report(flow, issues, "request")
+        except Exception as e:
+            print(f"[ERROR] Client Secret Check (request) failed: {e}")
+
+    def response(self, flow: http.HTTPFlow) -> None:
+        try:
+            if not self.is_oauth_uri(flow.request.url):
+                return
+            issues = self.check_client_secret_leak(flow)
+            if issues:
+                self._report(flow, issues, "response")
+        except Exception as e:
+            print(f"[ERROR] Client Secret Check (response) failed: {e}")
diff --git a/addon/init.py b/addon/init.py
index 78e616a..5b35835 100644
--- a/addon/init.py
+++ b/addon/init.py
@@ -4,6 +4,7 @@ from pkce_check import PKCEDowngradeChecker
 from ScopeDetection import ScopeDetection
 from csrf_check import CsrfChecker
 from nonce_check import NonceChecker
+from cleintsecret_check import ClientSecretChecker
 from redirect_uri_check import RedirectBypassChecker
 from access_token import AccessTokenScanner
 
@@ -64,6 +65,24 @@ class NonceAddon:
         except Exception as e:
             print(f"[ERROR] NonceAddon failed: {e}")
             pass
+        
+class ClientSecretAddon:
+    def __init__(self):
+        self.checker = ClientSecretChecker()
+
+    async def request(self, flow: http.HTTPFlow):
+        try:
+            self.checker.request(flow)
+        except Exception as e:
+            print(f"[ERROR] ClientSecretAddon request failed: {e}")
+            pass
+        
+    async def response(self, flow: http.HTTPFlow):
+        try:
+            self.checker.response(flow)
+        except Exception as e:
+            print(f"[ERROR] ClientSecretAddon response failed: {e}")
+            pass      
 
 class AccessTokenAddon:
     def __init__(self):
@@ -87,4 +106,4 @@ class RedirectBypassAddon:
         except Exception as e:
             print(f"[ERROR] RedirectBypass Addon failed: {e}")
 
-addons = [PKCEAddon(), ScopeAddon(), CsrfAddon(), NonceAddon(), AccessTokenAddon(), RedirectBypassAddon()]
+addons = [PKCEAddon(), ScopeAddon(), CsrfAddon(), NonceAddon(), ClientSecretAddon(), AccessTokenAddon(), RedirectBypassAddon()]