The following code is a simple example of using `cPickle` in order to generate an auth_token which is a serialized User object.
```python
import cPickle
from base64 import b64encode, b64decode
class User:
def __init__(self):
self.username = "anonymous"
self.password = "anonymous"
self.rank = "guest"
h = User()
auth_token = b64encode(cPickle.dumps(h))
print("Your Auth Token : {}").format(auth_token)
```
The vulnerability is introduced when a token is loaded from an user input.
```python
new_token = raw_input("New Auth Token : ")
token = cPickle.loads(b64decode(new_token))
print "Welcome {}".format(token.username)
```
Python 2.7 documentation clearly states Pickle should never be used with untrusted sources. Let's create a malicious data that will execute arbitrary code on the server.
> The pickle module is not secure against erroneous or maliciously constructed data. Never unpickle data received from an untrusted or unauthenticated source.
