👉 Overview
👀 What ?
An Open Redirect is a vulnerability that occurs when an application doesn’t correctly validate input and uses it to redirect the user to an external website. It is a type of unvalidated redirects and forwards vulnerability, which is in the OWASP’s 2013 Top 10 list of the most critical web application security risks.
🧐 Why ?
Open Redirect is an important issue because it can be used to carry out phishing attacks. An attacker can use it to craft a link that looks legitimate but actually redirects the user to a malicious site. This can trick the user into sharing sensitive information, such as their login credentials or credit card information. It can also be used to carry out other attacks, such as Cross-Site Scripting (XSS) and Cross-Site Request Forgery (CSRF).
⛏️ How ?
To prevent Open Redirect vulnerabilities, developers should avoid using user input to determine the destination of redirects whenever possible. If it is necessary to include user input in a redirect, the input should be validated against a list of safe URLs. Additionally, applications should use tokens to ensure that redirects cannot be manipulated.
⏳ When ?
Open Redirect vulnerabilities have been a common issue in web applications for many years. They began to receive more attention in the early 2000s, with the advent of phishing attacks. Despite efforts to educate developers about the dangers of unvalidated redirects and forwards, these vulnerabilities continue to be prevalent in modern web applications.
⚙️ Technical Explanations
An Open Redirect vulnerability exists when an application takes user input and uses it to construct a redirection URL without validating it. This can allow an attacker to craft a URL that will pass through the application's redirection mechanism and send the user to an arbitrary external site. The attacker's URL can be made to look like a legitimate URL for the application, which can trick the user into thinking they are still interacting with the trusted site. This can lead to various types of attacks, including phishing and the theft of sensitive information. The best way to prevent Open Redirect vulnerabilities is to avoid using user input in redirection URLs altogether. If that is not possible, the input should be validated against a list of safe URLs or whitelisted paths. Additionally, using tokens in redirects can prevent an attacker from manipulating the destination of the redirect.