A while ago Jonas Lykkegaard disclosed a zeroday that could be used to create files in the SYSTEM folder. CVE-2020-16885 got assigned for this vulnerability, and was since patched with KB4580346. This vulnerability was very convenient for Dynamic-link library (DLL) side-loading, which I will show in this blog post. Below you can find his original Twitter message.
Unprivileged users are not allowed to create files in system32 folder- on hyper-v hosts they finally realised that unprivileged lives matters too as anyone can now create files there , with creater as owner, just open like this: pic.twitter.com/Pd6nnqhcKZ