CVE-2026-66599: CWE-79 Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting') in Liquid Web / StellarWP WPComplete

CVE-2026-66599 is an unauthenticated Cross-Site Scripting (XSS) vulnerability in WPComplete versions <= 2.9.5.6. The flaw is due to improper neutralization of input during web page generation (CWE-79), which can lead to script injection. The vulnerability has a CVSS 3.1 score of 7.1, indicating high severity with network attack vector, low attack complexity, no privileges required, user interaction required, and impacts on confidentiality, integrity, and availability. No patch or official remediation level is currently documented.

Successful exploitation can allow an unauthenticated attacker to execute arbitrary scripts in the context of the affected web application, potentially leading to data disclosure, modification, or disruption of service. The vulnerability affects confidentiality, integrity, and availability as per the CVSS vector. However, no known exploits are reported in the wild at this time.

Patch status is not yet confirmed — check the vendor advisory for current remediation guidance. Until a fix is available, consider applying strict input validation and output encoding as temporary mitigations to reduce XSS risk. Monitor official Liquid Web / StellarWP channels for updates.