A missing validation check in Ghost CMS allowed users to redeem subscription offers that had already expired, enabling them to activate benefits or services that should no longer be available. This flaw is a classic input validation failure (CWE‑20) that undermines the integrity of the subscription logic and can result in unauthorized access or usage of paid features. The impact is primarily business‑logic abuse, which could erode revenue or bypass billing controls.

The vulnerability affects the Ghost content management system from versions 4.22.0 through 6.54.0 inclusive. All installations built on these releases carry the flaw until the security update in version 6.54.1 is applied. The issue does not pertain to other software vendors or products.

With a CVSS score of 4.8 the risk is moderate; the exploit requires that an attacker can trigger the offer‑redemption path, which is typically accessible by authenticated users of the CMS. No explicit remote or network attack vector is documented, so the likely attack scenario involves an authenticated content manager or automated script that can submit a redemption request. The EPSS score is not listed, and the vulnerability is not currently included in the CISA KEV catalog, indicating that it is not widely exploited in the field at this time.