Description

The Newsletters WordPress plugin before 4.17 does not generate its API key using a sufficiently random source, deriving it from a publicly known value, allowing unauthenticated attackers to compute the key and perform privileged actions such as adding and deleting subscribers and sending emails, when the optional API has been enabled.

Executive Summary

Technical Details

Mitigations

References

Additional Metadata

{
  "score": "4.8",
  "pubDate": "2026-08-29T06:17:12.177Z",
  "pubdate": "2026-08-29T06:17:12.177Z",
  "executiveSummary": "The Newsletters WordPress plugin prior to version 4.17 contains a critical vulnerability related to insufficient randomness in cryptographic key generation. This flaw allows unauthenticated attackers to predict and compute the API key used for securing the plugin's optional API interface.\nThe vulnerability type is categorized under broken authentication and insufficient entropy in security-sensitive components. Successful exploitation enables unauthorized actors to bypass authentication controls and gain administrative control over the plugin's core functions.\nThe impact includes the ability for remote, unauthenticated attackers to perform privileged actions, such as mass subscriber list manipulation, deletion of user data, and unauthorized transmission of emails via the plugin's infrastructure.\nThe risk is severe, as the API key is derived from publicly accessible metadata, rendering the authentication mechanism effectively transparent. Attackers require no prior credentials or elevated privileges, relying solely on their ability to reverse the key derivation process. The attack can be executed remotely over the network, posing a significant threat to data integrity and organizational communication channels.",
  "technicalDetails": "The root cause of the vulnerability lies in the implementation of the API key generation algorithm within the Newsletters plugin. Rather than utilizing a cryptographically secure pseudo-random number generator (CSPRNG) or a high-entropy secret, the plugin derives the API key using a publicly known value or a predictable seed. This lack of entropy results in a small keyspace that can be computed by an attacker.\nThe exploitation process involves identifying the publicly known input parameters that the plugin uses to derive the API key. Because the derivation logic is deterministic and relies on non-secret data, an attacker can replicate the calculation on their own infrastructure to derive the valid API key for a target installation. Once computed, the attacker can supply this key in API requests.\nThe attack flow proceeds as follows: First, the attacker identifies a target site running a vulnerable version of the Newsletters plugin where the API functionality has been enabled. Second, the attacker analyzes the client-side or server-side behavior to isolate the public value used as a seed for the key generation. Third, the attacker runs a local script to compute the corresponding API key based on the observed public values. Finally, the attacker crafts malicious HTTP requests, appending the computed key in the required headers or parameters to authenticate as a privileged user.\nThe vulnerable component is the API authentication module of the Newsletters plugin. Because the API is optional, this vulnerability only affects instances where the feature has been explicitly activated by the administrator. However, once enabled, the interface exposes sensitive subscriber management and email dispatch functions without robust security.\nThe post-exploitation impact allows for full control over the plugin's mailing list operations. Attackers can leverage this to exfiltrate subscriber databases, inject malicious content into outgoing emails, or delete existing mailing lists, leading to potential data loss or the misuse of the organization's email reputation for phishing or spam campaigns."
}