Midday EUVD-2026-66611

The caller must be an authenticated Midday user holding any membership in the target team, including the default Member role automatically assigned to all invited users - no elevated privilege is required. No special server configuration, feature flag, or non-default deployment mode is needed; the flaw is present in the standard team membership model for all Midday instances. Exploitation is limited to users who have already been invited to the team: unauthenticated external attackers cannot exploit this directly. The threat model is therefore insider threat or compromised Member-role accounts. No user interaction from the victim team owner or any other party is required once the attacker has their membership credential.

The CVSS 4.0 vector (AV:N/AC:L/AT:N/PR:L/UI:N/VC:N/VI:H/VA:H) and score of 7.2 accurately reflect the threat model: network-reachable with low complexity, requiring only low-privilege access (any team membership), producing high integrity and availability impact with no confidentiality component. No EPSS score was provided in the input data. There is no CISA KEV listing and no confirmed POC, placing this in a known-but-not-yet-weaponized state. However, exploitation complexity is extremely low for anyone already holding team membership - only knowledge of the API endpoint is required beyond the baseline credential. The secondary consequence of triggering bank-connection token usage against external financial providers meaningfully amplifies real-world impact beyond what the CVSS score alone conveys. This should be treated as a genuine operational priority for any Midday deployment with untrusted or externally invited team members, despite the absence of confirmed active exploitation.

An attacker invited to a Midday workspace as a standard Member - the default role for any invitee - authenticates to the application and calls the team delete tRPC procedure directly. Because the team-access helper confirms membership without verifying the owner role, the request succeeds: the team and all associated records are permanently deleted, and the backend enqueues a cleanup job that uses the team's stored bank-connection OAuth tokens against linked financial providers, potentially triggering unintended transactions or token revocation at those providers.