Description

The BlockSpare plugin for WordPress is vulnerable to authorization bypass due to incorrect logic in the permission callback in all versions up to, and including, 4.2.6 due to the use of an AND (&&) operator instead of an OR (||) operator. This makes it possible for authenticated attackers, with Subscriber-level access and above, to bypass authorization checks and create arbitrary posts.

Executive Summary

Technical Details

Mitigations

References

Additional Metadata

{
  "score": "4.3",
  "pubDate": "2026-09-19T08:16:53.200Z",
  "pubdate": "2026-09-19T08:16:53.200Z",
  "executiveSummary": "The BlockSpare plugin for WordPress, in all versions up to and including 4.2.6, contains a critical authorization bypass vulnerability.\nThe security flaw stems from flawed permission logic within the plugin's REST API endpoint handler, specifically an incorrect implementation of logical operators.\nThis vulnerability allows authenticated attackers with minimal privileges, such as Subscribers, to bypass intended access control mechanisms.\nBy successfully exploiting this vulnerability, an attacker can perform unauthorized actions, specifically the creation of arbitrary posts within the WordPress installation.\nThe risk implication is high, as it allows low-privileged users to elevate their capabilities to perform administrative-level actions.\nExploitation requires the attacker to hold at least a Subscriber-level account on the target WordPress site, making it an authenticated, internal threat vector.\nSuccessful exploitation compromises the integrity of the site's content management, as arbitrary posts can be created without legitimate authorization.",
  "technicalDetails": "The vulnerability originates in the plugin's REST API permission callback function, which is responsible for verifying if a requester possesses the necessary capabilities to perform specific actions.\nThe root cause is a logical error in the conditional statement used for access control validation. The implementation uses a logical AND (&&) operator where a logical OR (||) operator was intended.\nIn a secure implementation, permission checks typically ensure that a user has one of several required capabilities. By using an AND operator, the code logic demands that a user simultaneously possess multiple, potentially conflicting or mutually exclusive capabilities, or conversely, creates a flawed path where the condition defaults to granting access when it should restrict it.\nSpecifically, the flawed logic allows the authorization check to return true for users that should be restricted, enabling them to execute functions that are intended only for users with higher privileges, such as Authors, Editors, or Administrators.\nThe attack flow proceeds as follows: An authenticated user (e.g., a Subscriber) initiates a POST request to the affected REST API endpoint exposed by the BlockSpare plugin. The plugin intercepts the request and triggers the vulnerable permission callback function. Due to the improper logic operator, the callback incorrectly evaluates the user's current session and capabilities as sufficient to perform the requested action. The REST API handler subsequently proceeds to execute the post-creation routine, allowing the unauthorized user to inject new content into the database.\nThe vulnerable component is the permission callback function defined within the BlockSpare plugin, which manages authorization for REST API endpoints. This flaw affects all versions up to and including 4.2.6.\nThe post-exploitation impact includes unauthorized content creation, which could be used to facilitate further attacks such as Cross-Site Scripting (XSS) if the created content includes malicious scripts, or to deface the website, propagate spam, or perform SEO poisoning."
}