Cross-App Permission Stacking Creates Hidden Privilege Escalation Paths

Modern SaaS environments rarely fail because of a single over-permissioned integration. They fail because individually reasonable grants — a calendar read here, a Drive write there, a Slack webhook somewhere else — combine across apps and identities to form privilege paths that no single review would flag. These are toxic combinations: the OAuth token in App A reaches the data store in App B through a shared service account in App C, and nobody owns the composite risk.

The core problem is that permission reviews still happen app-by-app while attackers reason graph-by-graph. A marketing automation tool with contact-export scope plus a finance connector with read access plus a shared admin identity is not three medium risks; it is one path to customer PII and revenue data. Traditional IAM tooling treats each grant in isolation, and SSPM products only recently started correlating across tenants, apps, and non-human identities.

Defenders need continuous mapping of effective permissions across the full app graph, including service accounts, API tokens, and third-party integrations, with alerting tuned to composite exposure rather than individual scopes. Cleanup starts with killing stale non-human identities, scoping OAuth grants to least-privilege, and treating cross-app scope combinations as first-class findings in access reviews.