Installing plugins and themes on a WordPress site enhances its functionality but also introduces potential security risks that users should carefully consider. Prior to installation, it's advisable to research developers, check ratings and reviews, and investigate any past vulnerabilities associated with the plugin or theme to understand how issues were addressed. Security plugins like Wordfence, Bulletproof Security, and All In One WP Security & Firewall can help protect WordPress sites from various threats such as malware, XSS, and SQL injections, though they themselves have occasionally faced vulnerabilities. The key to maintaining a secure WordPress environment is not just in using these plugins but also in how swiftly and effectively vulnerabilities are managed and resolved.