Jira before 8.4.0 is susceptible to information disclosure. The /rest/api/latest/groupuserpicker resource can allow an attacker to enumerate usernames, and thereby potentially obtain sensitive information, modify data, and/or execute unauthorized operations.
id: CVE-2019-8449
info:
name: Jira <8.4.0 - Information Disclosure
author: harshbothra_
sever
...