SSRF stands for Server-Side Request Forgery. It is a web security vulnerability that allows an attacker to cause the server-side application to make requests to an unintended location. This could result in unauthorized access to data or services, or malicious attacks on other systems.
For example, imagine a web application that allows users to enter a URL and view the contents of that URL in the browser. If the application does not validate the user-supplied URL, an attacker could enter a URL that points to an internal system or service that is not accessible from the outside. This way, the attacker could access or manipulate sensitive information or resources on the internal system or service, such as files, databases, or APIs.
To prevent SSRF vulnerabilities, web applications should validate and sanitize the user-supplied URLs before making requests to them. They should also restrict the types and destinations of the requests that the application can make, and use firewall rules or network access control lists to block unwanted connections.