The /rest/api/latest/groupuserpicker resource in Jira before version 8.4.0 allows remote attackers to enumerate usernames via an information disclosure vulnerability.
Severity
CVSS 3.1
5.3 medium
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N
EPSS
85% chance of exploitation in the next 30 days; higher than 99% of CVEs (scores of 2026-10-31)