Update free-courses-en.md (#11534)

Author: dharminnagar

Diff for: courses/free-courses-en.md

@@ -337,6 +337,7 @@
 * [Ethereum Developer Bootcamp](https://www.alchemy.com/university/courses/ethereum) - Alchemy University
 * [Free Blockchain Development Courses](https://www.youtube.com/playlist?list=PLS5SEs8ZftgUNcUVXtn2KXiE1Ui9B5UrY) - Dapp University
 * [Learn Blockchain](https://www.youtube.com/playlist?list=PLlp912GlUiC1xPnwVmKgIiuMERetMwre9) - Roomyan
+* [Smart Contract Security](https://updraft.cyfrin.io/courses/security) - Cyfrin Updraft
 * [Solidity, Blockchain, and Smart Contract Course – Beginner to Expert Python Tutorial](https://www.youtube.com/watch?v=M576WGiDBdQ) - Patrick Collins (freeCodeCamp.org)