Complex sentence: When first proposed, there were concerns that this feature could be exploit as a security vulnerability (since addressed) and that although memory usage is reduced, CPU usage is increased, thus negating potential increases in performance.
Split into simpler sentences: When first proposed, there were concerns that this feature could be exploit as a security vulnerability (this concern has since been addressed). Another concern is that although memory usage is reduced, CPU usage is increased, thus negating potential increases in performance.