Update README.md

README.md

@@ -3,6 +3,10 @@ PoC for CVE-2021-3156 (sudo heap overflow). Exploit by @gf_256 aka cts. Thanks t
 
 [Demo video](https://twitter.com/gf_256/status/1355354178588180481)
 
+# Important note
+
+**The modified time of /etc/passwd needs to be newer than the system boot time, if it isn't you can use `chsh` to update it. Unfortunately this means you will have to know the password for the account you are running as. Remember that `chsh` doesn't accept empty passwords by default so if it is empty you may have to set one with `passwd`.**
+
 # Instructions
 
 1. wget/curl