![]() Force all redirects to first go through a page notifying users that they are going off of your site, and have them click a link to confirm.Sanitize input by creating a list of trusted URL's (lists of hosts or a regex).It is recommended that any such destination input be mapped to a value, rather than the actual URL or portion of the URL, and that server side code translate this value to the target URL.If user input can’t be avoided, ensure that the supplied value is valid, appropriate for the application, and is authorized for the user.In this case, you should have a method to validate URL. If used, do not allow the url as user input for the destination.Simply avoid using redirects and forwards.ASP.NET MVC 2 LogOn action in AccountController.cs (see Microsoft Docs link provided above for the context): public ActionResult LogOn(LogOnModel model, string returnUrl) Preventing Unvalidated Redirects and Forwards Safe use of redirects and forwards can be done in a number of ways: You can see that no validation is being performed against the returnUrl parameter. After a successful login, the controller returns a redirect to the returnUrl. The code for the LogOn action in an ASP.NET MVC 2 application is shown below. In order to avoid this vulnerability, you need to apply MVC 3. NET MVC 1 & 2 websites are particularly vulnerable to open redirection attacks. If no validation is applied, a malicious user could create a hyperlink to redirect your users to an unvalidated malicious website, for example: The user sees the link directing to the original trusted site ( ) and does not realize the redirection that could take place Dangerous URL Redirect Example 2 ASP. This vulnerability could be used as part of a phishing scam by redirecting users to a malicious site. NET Vulnerable Code: string url = request.QueryString Response.Redirect(url) And in Rails: redirect_to params The above code is vulnerable to an attack if no validation or extra method controls are applied to verify the certainty of the URL. Dangerous URL Redirect Example 1 The following Java code receives the URL from the parameter named url (GET or POST) and redirects to that URL: ndRedirect(request.getParameter("url")) The following PHP code obtains a URL from the query string (via the parameter named url) and then redirects the user to that URL: $redirect_url = $_GET header("Location: ". Dangerous URL Redirects The following examples demonstrate unsafe redirect and forward code. NET : Response.Redirect("~/folder/Login.aspx") Rails : redirect_to login_path In the examples above, the URL is being explicitly declared in the code and cannot be manipulated by an attacker. Unvalidated redirect and forward attacks can also be used to maliciously craft a URL that would pass the application’s access control check and then forward the attacker to privileged functions that they would normally not be able to access. Because the server name in the modified link is identical to the original site, phishing attempts may have a more trustworthy appearance. By modifying untrusted URL input to a malicious site, an attacker may successfully launch a phishing scam and steal user credentials. Unvalidated redirects and forwards are possible when a web application accepts untrusted input that could cause the web application to redirect the request to a URL contained within untrusted input.
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