Description

The Easy Appointments WordPress plugin through 3.12.26 does not correctly validate shortcode input in one of its block-rendering actions, checking only the first tag of the supplied string against an allowlist while rendering the entire string, allowing users with contributor-level access to execute arbitrary registered shortcodes.

Executive Summary

Technical Details

Mitigations

References

Additional Metadata

{
  "score": "2.7",
  "pubDate": "2026-08-06T22:16:46.173Z",
  "pubdate": "2026-08-06T22:16:46.173Z",
  "executiveSummary": "An input validation vulnerability exists within the Easy Appointments WordPress plugin through version 3.12.26, specifically localized to one of its block-rendering actions.\nThe vulnerability allows authenticated users with contributor-level privileges to execute arbitrary registered shortcodes via flawed string evaluation mechanisms.\nThe root flaw stems from the application checking only the initial tag of a supplied input string against a predefined allowlist, while subsequently rendering the entire supplied string payload.\nThe impact of this security deficiency encompasses potential privilege escalation, unauthorized data access, or execution of sensitive functionality exposed through registered shortcodes.\nExploitation requires contributor-level access to the WordPress site, enabling attackers to leverage existing shortcode capabilities beyond their intended authorization level.\nRisk implications include compromise of application integrity and potential exposure of underlying system components if administrative or high-privilege shortcodes are invoked improperly.",
  "technicalDetails": "The Easy Appointments WordPress plugin through version 3.12.26 contains a critical input validation flaw in its block-rendering functionality.\nThe vulnerable component is responsible for processing and rendering block-based content that incorporates shortcodes supplied by users.\nThe root cause of the vulnerability is improper validation logic applied to shortcode input strings.\nDuring the block-rendering action, the validation routine inspects only the very first tag of the supplied input string to determine if it complies with an allowlist.\nOnce the initial tag passes this superficial check, the application proceeds to render the entire supplied string, completely bypassing further validation for subsequent or embedded tags and payloads.\nAn attacker possessing contributor-level privileges can leverage this flaw by crafting a specialized input string where an allowlisted tag serves as a prefix, followed by arbitrary registered shortcodes.\nThe attack flow proceeds as follows: 1) The contributor-level user crafts a malicious payload containing a permitted initial shortcode tag followed by unauthorized shortcode invocations. 2) The user submits this payload to the vulnerable block-rendering action. 3) The plugin validates only the first tag, confirming it against the allowlist. 4) The plugin executes the entire string via WordPress shortcode parsing mechanisms. 5) Arbitrary registered shortcodes are evaluated and executed within the context of the application.\nAuthentication is required at the contributor level, and the attack surface is exposed via the web application interface handling block rendering.\nPost-exploitation impact depends heavily on the capabilities exposed by other plugins or themes registered via shortcodes within the WordPress environment, potentially allowing unauthorized data retrieval or execution of sensitive operations."
}