CVE-2026-105860: Payload has a tenant authorization bypass in Multi-Tenant Plugin

## Impact When using the default tenant array field access, an authenticated user could assign themselves to other tenants. **You are affected if:** - You are using `@payloadcms/plugin-multi-tenant` If you configure the tenants arrayFieldAccess.create/update functions, a secured replacement membership field, you are not affected by this specific default behavior. ## Patches Users should upgrade Payload packages to `>= 3.90.0` or `>= 4.0.0-canary.34`. ## Workarounds Configure tenants arrayFieldAccess.create and tenants arrayFieldAccess.update so only trusted users authorized for all tenants can modify memberships.