diff --git a/js_security_test.js b/js_security_test.js
new file mode 100644
index 0000000000..f883fb20c8
--- /dev/null
+++ b/js_security_test.js
@@ -0,0 +1,53 @@
+function renderHtmlVulnerable(userInput) {
+    const output = document.getElementById('user-content-area');
+    if (output) {
+        output.innerHTML = userInput;
+    }
+}
+
+function renderHtmlSafe(userInput) {
+    const output = document.getElementById('user-content-area');
+    if (output) {
+        output.textContent = userInput;
+    }
+}
+
+function executeCodeVulnerable(userInput) {
+    console.log("Executing vulnerable code...");
+    eval(userInput);
+}
+
+function processDataSafe(userInput) {
+    try {
+        const data = JSON.parse(userInput);
+        console.log("Safely processed data:", data);
+    } catch (e) {
+        console.error("Input is not valid JSON.");
+    }
+}
+
+function checkRedosVulnerable(input) {
+    const re = /^(a+)+$/;
+    return re.test(input);
+}
+
+function checkRedosSafe(input) {
+    const re = /^a+$/;
+    return re.test(input);
+}
+
+
+function main() {
+    const maliciousHtml = "<img src=x onerror=alert('XSS')>";
+    const maliciousCode = "alert('Code Injection');";
+
+    renderHtmlVulnerable(maliciousHtml);
+    renderHtmlSafe(maliciousHtml);
+
+    processDataSafe('{"status": "ok"}');
+
+    checkRedosVulnerable("a".repeat(20) + "b");
+    checkRedosSafe("a".repeat(20) + "b");
+}
+
+main();
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