Web applications are prone to hacking because web developers are often not well-versed in security issues. The top web vulnerabilities are cross-site scripting (XSS), SQL injection, input validation issues, and remote file inclusion. XSS attacks involve injecting malicious code into web pages through user input. SQL injection occurs when user input is not sanitized before being used in SQL queries, allowing attackers to alter queries. Proper input validation and sanitization on both the client- and server-sides are needed to prevent many security bugs. Browser vulnerabilities can also potentially expose issues in web applications if not properly designed with security in mind. Constant vigilance is required to address new attacks and protect applications and users.