Always validate security-critical inputs to prevent DoS attacks and injection vulnerabilities. Implement size limits, scheme restrictions, and format validation for user-controlled data that affects security mechanisms. Key practices: - Set reasonable size limits (e.g., 4KB for cookie values) to prevent DoS through oversized inputs - Validate URL schemes for security-sensitive operations (only allow http/https for proxies) - Follow standard library patterns for input sanitization and validation - Avoid logging sensitive input values that could be exploited Example implementation: ```go // Validate proxy URL scheme pURL, err := urlPkg.Parse(proxyURL) if err != nil { return err } if pURL.Scheme != "http" && pURL.Scheme != "https" { return errors.New("unsupported proxy scheme") } // Limit cookie value size to prevent DoS func (c *DefaultCtx) sanitizeCookieValue(v string) string { const maxCookieSize = 4096 // 4KB limit if len(v) > maxCookieSize { // Log generic message without exposing value log.Warn("cookie value exceeds size limit, truncating") v = v[:maxCookieSize] } // Continue with sanitization... } ``` This prevents common attack vectors while maintaining functionality and following security best practices established in standard libraries.