As part of WDigest authentication provider, Windows versions up to 8 and 2012 used to store logon credentials in memory in plaintext by default, which is no longer the case with newer Windows versions.
It is still possible, however, to force WDigest to store secrets in plaintext.
Let's first make sure that wdigest is not storing credentials in plaintext on our target machine running Windows 10:
Note the password field is null:
Now as an attacker, we can modify the following registry key to force the WDigest to store credentials in plaintext next time someone logs on to the target system:
reg add HKLM\SYSTEM\CurrentControlSet\Control\SecurityProviders\WDigest /v UseLogonCredential /t REG_DWORD /d 1
Say, now the victim on the target system spawned another shell:
runas /user:mantvydas powershell
Running mimikatz for wdigest credentials now reveals the plaintext password of the victim user