Update README.md

Author: ohJohanZ

open-report-V2/README.md

@@ -10,6 +10,7 @@ Some open security audit reports of SlowMist.
 - [QuarkChain Security Audit Report](https://github.com/slowmist/Knowledge-Base/tree/master/open-report-V2/blockchain/SlowMist%20Audit%20Report%20-%20QuarkChain_en-us)
 - [Vexanium Security Audit Report](https://github.com/slowmist/Knowledge-Base/tree/master/open-report-V2/blockchain/SlowMist%20Audit%20Report%20-%20Vexanium_en-us.pdf)
 - [WaykiChain Security Audit Report](https://github.com/slowmist/Knowledge-Base/tree/master/open-report-V2/blockchain/SlowMist%20Audit%20Report%20-%20WaykiChain_en-us.pdf)
+- [Bifrost Security Audit Report](https://github.com/slowmist/Knowledge-Base/blob/master/open-report-V2/blockchain/SlowMist%20Audit%20Report%20-%20Bifrost.pdf)
 
 ### Blockchain application security audit open reports
 - [ABCWallet Security Audit Report](https://github.com/slowmist/Knowledge-Base/tree/master/open-report-V2/blockchain-application/SlowMist%20Audit%20Report%20-%20ABCWallet_en-us.pdf)