The on_get_missing_events
function in handlers/federation.py in Matrix Synapse before 0.31.1 has a security bug in the getmissingevents federation API where event visibility rules were not applied correctly.
{ "nvd_published_at": "2018-06-13T14:29:00Z", "cwe_ids": [], "severity": "HIGH", "github_reviewed": true, "github_reviewed_at": "2023-07-21T22:50:51Z" }