Client-Side Vulnerabilities

1 min read Security Careers & Certifications

Client-Side Vulnerabilities

Cross-site scripting (XSS) vulnerabilities enable session theft, phishing, and browser exploitation. Test every reflection point including parameters, headers, and error messages. Use polyglot payloads testing multiple contexts simultaneously. Bypass filters through encoding, case variations, and browser parsing quirks. While OSCP focuses on system compromise rather than client attacks, XSS sometimes enables administrative session theft or combines with CSRF for privileged actions.

Client-side validation bypass reveals server-side processing assumptions. Disable JavaScript validation, modify hidden fields, and test disabled form elements. Applications trusting client-side controls for security frequently contain serious vulnerabilities. Browser developer tools enable easy manipulation of any client-side restrictions.

JavaScript analysis reveals sensitive information and hidden functionality. Obfuscated code might hide API keys, internal endpoints, or business logic. Development comments sometimes contain credentials or internal information. WebPack source maps expose original source code structure. Patient JavaScript analysis frequently reveals vulnerabilities or information accelerating exploitation.