In May 2018 Microsoft patched an interesting vulnerability (CVE-2018-0824) which was reported by Nicolas Joly of Microsoft's MSRC:
A remote code execution vulnerability exists in "Microsoft COM for Windows" when it fails to properly handle serialized objects. An attacker who successfully exploited the vulnerability could use a specially crafted file or script to perform actions. In an email attack scenario, an attacker could exploit the vulnerability by sending the specially crafted file to the user and convincing the user to open the file. In a web-based attack scenario, an attacker could host a website (or leverage a compromised website that accepts or hosts user-provided content) that contains a specially crafted file that is designed to exploit the vulnerability. However, an attacker would have no way to force the user to visit the website. Instead, an attacker would have to convince the user to click a link, typically by way of an enticement in an email or Instant Messenger message, and then convince the user to open the specially crafted file. The security update addresses the vulnerability by correcting how "Microsoft COM for Windows" handles serialized objects.
The keywords "COM" and "serialized" pretty much jumped into my face when the advisory came out. Since I had already spent several months of research time on Microsoft COM last year I decided to look into it. Although the vulnerability can result in remote code execution, I'm only interested in the privilege escalation aspects.
Proof of Concept: