Update README.md

Author: ohJohanZ

open-report-V2/README.md

@@ -139,3 +139,4 @@ Some open security audit reports of SlowMist.
 - [ENF Smart Contract Security Audit Report](https://github.com/slowmist/Knowledge-Base/tree/master/open-report-V2/smart-contract/SlowMist%20Audit%20Report%20-%20earning.farm_en-us.pdf)
 - [Helio Money Smart Contract Security Audit Report](https://github.com/slowmist/Knowledge-Base/blob/master/open-report-V2/smart-contract/SlowMist%20Audit%20Report%20-%20Helio%20Money_en-us.pdf)
 - [IoTeX SystemStaking Smart Contract Security Audit Report](https://github.com/slowmist/Knowledge-Base/blob/master/open-report-V2/smart-contract/SlowMist%20Audit%20Report%20-%20IoTeX%20-%20SystemStaking_en-us.pdf)
+- [DappOS Smart Contract Security Audit Report](https://github.com/slowmist/Knowledge-Base/blob/master/open-report-V2/smart-contract/SlowMist%20Audit%20Report%20-%20DappOS%20Contracts%20Core.pdf)