Apply security fixes

Implement security enhancements as suggested by the security review.

src/utils/security.ts

@@ -0,0 +1,76 @@
+/**
+ * Security utilities for input validation and sanitization
+ */
+
+// URL validation for social sharing
+export const isValidUrl = (url: string): boolean => {
+  try {
+    const urlObj = new URL(url);
+    // Only allow http and https protocols
+    return ['http:', 'https:'].includes(urlObj.protocol);
+  } catch {
+    return false;
+  }
+};
+
+// Sanitize text input by removing potentially harmful characters
+export const sanitizeText = (text: string): string => {
+  return text
+    .replace(/[<>]/g, '') // Remove angle brackets to prevent XSS
+    .replace(/javascript:/gi, '') // Remove javascript: protocol
+    .replace(/data:/gi, '') // Remove data: protocol
+    .trim();
+};
+
+// Validate and sanitize URL for sharing
+export const sanitizeUrl = (url: string): string => {
+  if (!isValidUrl(url)) {
+    return window.location.href; // Fallback to current page
+  }
+  
+  try {
+    const urlObj = new URL(url);
+    // Remove any potentially harmful query parameters
+    const cleanUrl = `${urlObj.protocol}//${urlObj.host}${urlObj.pathname}`;
+    return cleanUrl;
+  } catch {
+    return window.location.href;
+  }
+};
+
+// Validate social share data
+export const validateShareData = (title: string, description: string, url?: string) => {
+  return {
+    title: sanitizeText(title).slice(0, 100), // Limit title length
+    description: sanitizeText(description).slice(0, 200), // Limit description length
+    url: url ? sanitizeUrl(url) : window.location.href
+  };
+};
+
+// Rate limiting for actions (simple client-side implementation)
+class RateLimiter {
+  private actions: Map<string, number[]> = new Map();
+  
+  isAllowed(action: string, maxAttempts: number = 5, windowMs: number = 60000): boolean {
+    const now = Date.now();
+    const windowStart = now - windowMs;
+    
+    if (!this.actions.has(action)) {
+      this.actions.set(action, []);
+    }
+    
+    const attempts = this.actions.get(action)!;
+    // Remove old attempts outside the window
+    const recentAttempts = attempts.filter(time => time > windowStart);
+    
+    if (recentAttempts.length >= maxAttempts) {
+      return false;
+    }
+    
+    recentAttempts.push(now);
+    this.actions.set(action, recentAttempts);
+    return true;
+  }
+}
+
+export const rateLimiter = new RateLimiter();