Attack Vectors

CVE-2025-14799 affects the WordPress plugin “Brevo – Email, SMS, Web Push, Chat, and more.” (slug: mailin) in versions up to and including 3.3.0. It is rated Medium severity (CVSS 6.5).

The primary exposure is through a public-facing WordPress site where the plugin is installed. An unauthenticated attacker can target the plugin’s REST API endpoint /wp-json/mailin/v1/mailin_disconnect and exploit an authorization bypass by supplying a boolean true value for the id parameter, allowing actions without being logged in.

Security Weakness

The issue is caused by a validation mistake commonly referred to as “type juggling.” In the vulnerable versions, the plugin uses a loose comparison (==) instead of a strict comparison (===) when checking the installation ID in the disconnect endpoint. This can allow values that should not match to be treated as valid.

Because the endpoint is accessible without authentication and the validation can be bypassed, the control intended to prevent unauthorized disconnect actions is weakened, creating a pathway for external tampering with the Brevo integration settings.

Technical or Business Impacts

If exploited, an attacker can disconnect the Brevo integration and trigger disruptive changes, including deleting the API key, removing subscription forms, and resetting plugin settings. For marketing and revenue operations, this can translate into immediate lead-capture losses, broken campaign workflows, and gaps in subscriber acquisition.

Business risk includes reduced conversion performance (forms removed), reporting and attribution blind spots (data flows interrupted), and potential compliance and brand concerns if opt-in collection processes are unexpectedly disabled. While the CVSS indicates no direct confidentiality impact, integrity and availability impacts can be significant for marketing operations and customer communications.

Recommended remediation is to update the plugin to version 3.3.1 or a newer patched version, as advised by the source disclosure. For reference, see the CVE record: https://www.cve.org/CVERecord?id=CVE-2025-14799.

Similar Attacks

Authorization bypass issues in public-facing web components are a common cause of business disruption. Here are a few well-known examples where attackers leveraged weak access controls or exposed interfaces:

Microsoft Exchange “ProxyShell” exploitation (CISA alert) — attackers abused exposed server functionality to gain unauthorized access and disrupt operations.

Accellion FTA exploitation (CISA alert) — a vulnerable internet-facing component led to unauthorized actions and broad business impact.

CISA guidance on exploitation of remote access software vulnerabilities — highlights how attackers frequently target externally exposed services to bypass controls and trigger operational disruption.