JIRA v7.0.0-rc3#70105. Same scenario worked fine on all other EAP versions.

1. Create project
2. Use a specific issue security scheme
3. Use Default Issue Type Scheme
4. Use Default Issue Type Screen Scheme
5. Use System Default Field Configuration
6. Verify Security level is on the default screen
7. Create issue in this project - no Security Level field on screen
8. Update issue in this project - no Security Level field on screen

Another scenario

1. Create a Basic Software Development project
2. Set the issue security scheme to a specific scheme
3. Verify Security Level is on the default screen
4. Create issue - no Security Level field on the create screen
5. Update issue - no Security Level field on the edit screen