Parse Server before 8.6.93 and 9.0.0 before 9.10.1-alpha.13 does not enforce identity-scoped protectedFields (authenticated, role, or per-user groups) on count queries using the $relatedTo operator, exposing the size of protected Relation fields. An authenticated user who can read the owning object can combine counts with an objectId constraint as a membership oracle to reveal confidential memberships such as private groups or block lists.
{
"cna_assigner": "VulnCheck",
"cwe_ids": [
"CWE-639"
],
"osv_generated_from": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/109xxx/CVE-2026-109303.json"
}{
"extracted_events": [
{
"introduced": "9.0.0"
},
{
"fixed": "9.10.1-alpha.13"
},
{
"introduced": "0"
},
{
"fixed": "8.6.93"
}
],
"source": "AFFECTED_FIELD"
}