curl --location --request GET '/rest/api/3/project//issuesecuritylevelscheme'
{"defaultSecurityLevelId":10021,"description":"Description for the default issue security scheme","id":10000,"levels":[{"description":"Only the reporter and internal staff can see this issue.","id":"10021","name":"Reporter Only","self":"https://your-domain.atlassian.net/rest/api/3/securitylevel/10021"}],"name":"Default Issue Security Scheme","self":"https://your-domain.atlassian.net/rest/api/3/issuesecurityschemes/10000"}