diff --git a/rules/001_project_settings/001_0009_strict_mode_with_react_client.js b/rules/001_project_settings/001_0009_strict_mode_with_react_client.js
new file mode 100644
index 0000000..ef83947
--- /dev/null
+++ b/rules/001_project_settings/001_0009_strict_mode_with_react_client.js
@@ -0,0 +1,75 @@
+const metadata = {
+  scope: "package",
+  title: "Ensure strict mode is enabled when using the React client",
+  description:
+    "When React is enabled in Project Settings, StrictMode must also be enabled in Project Security for security and stability",
+  authors: ["Jurre Tanja <jurre.tanja@siemens.com>"],
+  custom: {
+    category: "Security",
+    rulename: "StrictModeWithReactClient",
+    severity: "HIGH",
+    rulenumber: "001_0009",
+    remediation: "Enable Strict mode in the Security settings",
+    input: ".*\\$ProjectSettings\\.yaml",
+  },
+};
+
+function rule(input = {}) {
+  const errors = [];
+
+  try {
+    // Navigate into Settings array to find UseOptimizedClient
+    let useOptimizedClient = undefined;
+
+    if (input.Settings && Array.isArray(input.Settings)) {
+      // Find the Forms$WebUIProjectSettingsPart section
+      const webUISettings = input.Settings.find(
+        (s) => s.$Type === "Forms$WebUIProjectSettingsPart",
+      );
+      if (webUISettings) {
+        useOptimizedClient = webUISettings.UseOptimizedClient;
+      }
+    }
+
+    // Check if UseOptimizedClient is enabled
+    if (useOptimizedClient === true || useOptimizedClient === "Yes") {
+      // Read the ProjectSecurity.yaml file to check StrictMode
+      try {
+        const securityContent = mxlint.io.readfile(
+          "Security$ProjectSecurity.yaml",
+        );
+
+        if (securityContent) {
+          // Parse the YAML string to find StrictMode value
+          const strictModeMatch =
+            securityContent.match(/^StrictMode:\s*(.+)$/m);
+          let strictModeValue = null;
+
+          if (strictModeMatch) {
+            const value = strictModeMatch[1].trim();
+            strictModeValue = value === "true" || value === true;
+          }
+
+          // Check if StrictMode is enabled
+          if (strictModeValue !== true) {
+            errors.push(`[${metadata.custom.severity}, ${metadata.custom.category}, ${metadata.custom.rulenumber}] StrictMode must be enabled in Project Security when UseOptimizedClient is enabled in Project Settings. Current
+   StrictMode value: ${strictModeValue}`);
+          }
+        }
+      } catch (securityError) {
+        errors.push(
+          `[${metadata.custom.severity}, ${metadata.custom.category}, ${metadata.custom.rulenumber}] Failed to read Security$ProjectSecurity.yaml: ${securityError.message}`,
+        );
+      }
+    }
+  } catch (e) {
+    errors.push(
+      `[${metadata.custom.severity}, ${metadata.custom.category}, ${metadata.custom.rulenumber}] Error checking strict mode configuration: ${e.message}`,
+    );
+  }
+
+  return {
+    allow: errors.length === 0,
+    errors,
+  };
+}
diff --git a/rules/001_project_settings/001_0009_strict_mode_with_react_client_test.yaml b/rules/001_project_settings/001_0009_strict_mode_with_react_client_test.yaml
new file mode 100644
index 0000000..3219eb3
--- /dev/null
+++ b/rules/001_project_settings/001_0009_strict_mode_with_react_client_test.yaml
@@ -0,0 +1,28 @@
+TestCases:
+  - name: allow when UseOptimizedClient is false
+    allow: true
+    input:
+      UseOptimizedClient: false
+    files:
+      "Security$ProjectSecurity.yaml":
+        StrictMode: false
+  - name: allow when both UseOptimizedClient and StrictMode are true
+    allow: true
+    input:
+      UseOptimizedClient: true
+    files:
+      "Security$ProjectSecurity.yaml":
+        StrictMode: true
+  - name: do not allow UseOptimizedClient true but StrictMode false
+    allow: false
+    input:
+      UseOptimizedClient: true
+    files:
+      "Security$ProjectSecurity.yaml":
+        StrictMode: false
+  - name: do not allow UseOptimizedClient true but StrictMode missing
+    allow: false
+    input:
+      UseOptimizedClient: true
+    files:
+      "Security$ProjectSecurity.yaml": {}
diff --git a/rules/002_domain_model/002_0008_avoid_read_write_default_access_rule.rego b/rules/002_domain_model/002_0008_avoid_read_write_default_access_rule.rego
index 17e2f39..f9e078e 100644
--- a/rules/002_domain_model/002_0008_avoid_read_write_default_access_rule.rego
+++ b/rules/002_domain_model/002_0008_avoid_read_write_default_access_rule.rego
@@ -3,7 +3,7 @@
 # title: Avoid using default read write access
 # description: This can lead to wrong set access rights
 # authors:
-# - Jurre Tanja <jurre.tanja@mendix.com>
+# - Jurre Tanja <jurre.tanja@siemens.com>
 # - Bart Zantingh <bart.zantingh@nl.abnamro.com>
 # related_resources:
 # - https://docs.mendix.com/refguide/access-rules/