curl --location --request GET '/rest/api/3/issuesecurityschemes/level'
{"isLast":true,"maxResults":50,"startAt":0,"total":1,"values":[{"description":"Only the reporter and internal staff can see this issue.","id":"10021","isDefault":true,"issueSecuritySchemeId":"10001","name":"Reporter Only","self":"https://your-domain.atlassian.net/rest/api/3/issuesecurityscheme/level?id=10021"}]}