CVE-2026-88782 in Kubio AI Page Builder Plugin
Summary
by MITRE • 10/03/2026
The Kubio AI Page Builder WordPress plugin before 2.9.3 does not validate the URI scheme of a user-supplied value before outputting it as a link target, allowing users with the contributor role and above to store a payload which executes in the browser of anyone who follows the link, including an administrator previewing the unpublished submission.
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Analysis
by VulDB Data Team • 10/03/2026
The vulnerability identified in Kubio AI Page Builder for WordPress prior to version 2.9.3 represents a significant security flaw rooted in insufficient input validation and improper output encoding. Specifically, the plugin fails to validate or sanitize the URI scheme of user-supplied values before incorporating them into HTML link targets. This oversight allows attackers with contributor-level permissions or higher to inject malicious Uniform Resource Identifiers that deviate from standard protocols such as HTTP or HTTPS. By exploiting this lack of validation, an attacker can construct a payload using the javascript: URI scheme, which instructs web browsers to execute arbitrary JavaScript code rather than navigating to a new page. This type of vulnerability is classically categorized under CWE-79, known as Cross-Site Scripting (XSS), specifically reflecting improper neutralization of input during web page generation.
The operational impact of this flaw extends beyond simple script execution due to the specific context in which it occurs. Because the vulnerable code handles link targets that may be previewed by administrators before publication, the attack vector is particularly potent. An administrator with elevated privileges can inadvertently trigger the malicious payload simply by viewing a draft or unpublished submission created by a lower-privileged user. This scenario transforms what might otherwise be a stored XSS vulnerability into an effective privilege escalation path. The attacker does not need to trick a high-privilege user into clicking a link on a public-facing page; instead, the mere act of previewing content within the administrative interface is sufficient to execute the code in the context of the administrator's session. This aligns with ATT&CK technique T1059, Command and Scripting Interpreter, as it enables the execution of arbitrary scripts that can lead further into lateral movement or data exfiltration phases of an attack lifecycle.
From a technical perspective, the root cause lies in the failure to enforce strict allow-listing for URI schemes during the sanitization process. Secure coding practices dictate that any user input destined for use as a link target must be validated against a predefined list of safe protocols. The absence of this check permits the injection of dangerous schemes like javascript:, data:, or vbscript:. When the browser parses these links, it interprets them as executable commands rather than navigational elements. This behavior is consistent with CWE-601, URL Redirection to Untrusted Site, although in this specific instance, the redirection leads directly to script execution within the current domain context due to the javascript: scheme. The vulnerability highlights a common deficiency in WordPress plugin development where input validation is often overlooked for fields that are perceived as low-risk or internal-use only.
Mitigation strategies must address both immediate remediation and long-term defensive posture. The primary solution is to upgrade the Kubio AI Page Builder plugin to version 2.9.3 or later, where this specific validation logic has been corrected. For organizations unable to patch immediately due to compatibility constraints, a temporary workaround involves restricting user roles that can create content with link targets until an update is applied. Additionally, implementing Content Security Policy headers can provide a layer of defense by restricting the sources from which scripts are allowed to execute, thereby mitigating the impact even if XSS occurs. Developers should also adopt rigorous input validation standards, ensuring that all URI schemes are explicitly checked against an allow-list containing only safe protocols such as http and https before being rendered in HTML attributes. This approach aligns with OWASP guidelines for preventing cross-site scripting by enforcing strict output encoding and input validation principles across the application lifecycle.