https://t.co/1Of8EsOW8z Here's a low quality bug that is a pain to exploit.. still unpatched. I'm done with all this anyway. Probably going to get into problems because of being broke now.. but whatever.
— SandboxEscaper (@SandboxEscaper) October 23, 2018
SandboxEscaper, a researcher who back in August tweeted out a Windows privilege escalation bug, has published another unpatched Windows flaw on Twitter.
The new bug has some similarities to the previous bug. Windows services usually run with elevated privileges. Sometimes they perform actions on behalf of a user, and to do this they use a feature called impersonation. These services act as if they were using a particular user's set of privileges. After they've finished that action, they revert to their normal, privileged identity.
Both this bug and SandboxEscaper's previous bug depend on improper use of impersonation—specifically, the services in question (last time it was Task Scheduler, this time it's the "Data Sharing Service") revert their impersonation too quickly and end up performing some actions with elevated privileges when they should in fact have been impersonated. The last bug allowed one file to be written over another. In this case, it's a call to delete a file that is improperly impersonated, ultimately giving regular unprivileged user the ability to delete any file on the system, even those that they should have no access to.