A Security Kernel Based on the Lambda Calculus from 1996 (http://mumble.net/~jar/pubs/secureos/secureos.html)
I've been reading up on the object capability security model a lot recently, and was pointed to this paper... I was hooked. A really compelling security model almost from first principles.
From this year I really liked the paper, Recovering Purity with Comonads and Capabilities, Vikraman Chaudhury and Neel Krishnaswami,
https://arxiv.org/abs/1907.07283