CSRF, or Cross-Site Request Forgery, is a type of security vulnerability that allows an attacker to trick a user into executing unwanted actions on a web application where they are authenticated. This can happen when a user is logged into a site and unknowingly clicks on a malicious link or visits a compromised page, causing their browser to send unauthorized requests to the target site. To protect against CSRF attacks, developers can implement various security measures, such as using anti-CSRF tokens, which are unique identifiers that validate requests. Additionally, ensuring that sensitive actions require user confirmation can help mitigate the risks associated with this vulnerability.