CVE-2026-87965 in Easy Appointments Plugin
Summary
by MITRE • 09/18/2026
The Easy Appointments WordPress plugin before 4.0.2.2 does not use an unguessable token to authorize its mail-link appointment cancellation and confirmation action, deriving the token from a hardcoded source-embedded salt and the appointment's creation timestamp, so unauthenticated attackers who know or guess that timestamp can cancel or confirm arbitrary appointments.
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Analysis
by VulDB Data Team • 09/18/2026
The vulnerability identified in Easy Appointments versions prior to 4.0.2.2 represents a critical failure in access control mechanisms for sensitive administrative actions within the WordPress ecosystem. The core issue stems from an insecure implementation of token-based authentication for mail-link appointment cancellation and confirmation operations. Instead of generating cryptographically secure, random tokens that are unpredictable and unique per session or action, the plugin derives its authorization tokens using a deterministic method involving a hardcoded salt embedded in the source code combined with the timestamp of when the appointment was created. This design choice fundamentally undermines the security model because it relies on secrecy through obscurity rather than true cryptographic randomness, creating a predictable attack surface for malicious actors.
From a technical perspective, the flaw allows unauthenticated attackers to forge valid authorization tokens if they possess knowledge or can accurately guess the creation timestamp of a target appointment. Since the salt is hardcoded and static across all installations using this version of the plugin, it does not provide any unique protection per instance. The only variable component in the token generation process is the appointment's creation time. If an attacker can determine when an appointment was scheduled—through public calendar views, email notifications intercepted via man-in-the-middle attacks, or other side-channel information—they can compute the exact same token used by the legitimate system to authorize changes to that appointment. This effectively bypasses any intended authentication checks, allowing external parties to execute privileged actions without valid credentials.
The operational impact of this vulnerability is severe and directly affects data integrity and user privacy within WordPress sites utilizing Easy Appointments. An attacker who successfully exploits this flaw can cancel existing appointments or confirm pending ones arbitrarily. In a business context, unauthorized cancellation leads to lost revenue, disrupted schedules, and potential reputational damage due to perceived unreliability. Conversely, the ability to force-confirm appointments could lead to double-booking conflicts, resource exhaustion, or harassment of service providers and clients by forcing unwanted interactions. Because these actions are triggered via mail links often shared with legitimate users, an attacker can craft malicious URLs that appear authentic but carry forged tokens, tricking the system into executing destructive commands under the guise of a normal user action.
This vulnerability aligns closely with CWE-287 Improper Authentication and CWE-345 Insufficient Verification of Data Authenticity as defined by common weakness enumerations standards. The failure to use unpredictable values for security-critical operations is also characteristic of weaknesses found in MITRE ATT&CK technique T1098, specifically Account Manipulation or Access Token Modification variants where attackers exploit weak token generation to gain unauthorized access. Furthermore, it reflects poor adherence to OWASP guidelines regarding secure session management and anti-CSRF protections, which mandate that all state-changing actions must be protected by unique, unpredictable tokens tied to the user's current session rather than static data derived from public or semi-public fields like timestamps.
To mitigate this vulnerability, organizations running Easy Appointments on WordPress should immediately update the plugin to version 4.0.2.2 or later, where the developers have addressed these authentication flaws by implementing proper cryptographic token generation mechanisms. Until an upgrade is feasible, administrators can consider disabling public appointment visibility features that expose creation timestamps if such functionality is not strictly required for business operations. Additionally, enforcing HTTPS across all site traffic helps prevent man-in-the-middle attacks that might allow attackers to intercept mail links and extract timestamp data more easily. Regular security audits of third-party plugins are essential to ensure they adhere to modern standards for secure coding practices, particularly regarding authentication tokens and access control logic.