CVE-2026-88783 in AI Page Builder Plugin
Summary
by MITRE • 10/03/2026
The Kubio AI Page Builder WordPress plugin before 2.9.3 does not limit its widening of the allowed HTML elements to the editor context, so the wider set is applied when filtering content submitted by unauthenticated users as well, allowing them to store markup which the Kubio AI Page Builder WordPress plugin before 2.9.3's own script later executes in the browser of any visitor, or of an administrator reviewing the still-unapproved submission.
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Analysis
by VulDB Data Team • 10/03/2026
The vulnerability identified within the Kubio AI Page Builder WordPress plugin prior to version 2.9.3 represents a critical failure in input validation and context-aware sanitization logic. This flaw stems from an improper implementation of HTML filtering mechanisms, where the scope of allowed elements is not correctly confined to the intended editor environment. In secure web application design, particularly within content management systems like WordPress, it is imperative that strict separation exists between trusted administrative contexts and untrusted user inputs. The plugin fails to enforce this boundary, resulting in a scenario where security controls designed for authenticated editors are inadvertently applied to data submitted by anonymous or unauthenticated users during the initial submission phase.
From a technical perspective, the core issue lies in how the sanitization function processes incoming content. Instead of applying restrictive whitelists that limit HTML tags and attributes to safe subsets suitable for public display, the plugin utilizes a broader set of allowed elements intended for the backend editor interface. This architectural oversight means that when an unauthenticated user submits content through the page builder form, the system does not strip potentially dangerous markup such as script tags or event handlers. Consequently, this maliciously crafted HTML is stored directly in the database without adequate sanitization, preserving its executable nature until it is rendered by a browser.
The operational impact of this vulnerability is severe, primarily manifesting as an Unrestricted Upload of Web-Content with Executable Functionality, which effectively leads to Stored Cross-Site Scripting. An attacker can craft a submission containing malicious JavaScript payloads embedded within HTML elements that are erroneously permitted by the flawed filter. Once stored, these scripts become persistent threats rather than transient session-based attacks. The execution context varies depending on who interacts with the submitted content first. If an administrator or editor reviews and approves the unapproved submission before it is published to the live site, they will inadvertently execute the malicious script within their own browser session while managing the website backend.
Furthermore, even if the content remains in a pending state, any visitor viewing the preview or draft version of the page may trigger the execution of these scripts. This dual-vector impact amplifies the risk significantly, as it compromises not only the administrative accounts responsible for site management but also the general audience visiting the public-facing portions of the website that might display unapproved drafts or previews. The persistence of this code in the database ensures that every subsequent view by any user serves as a potential attack vector, leading to session hijacking, credential theft, defacement, or redirection to malicious external sites.
This vulnerability aligns with Common Weakness Enumeration (CWE) identifiers such as CWE-79, which describes Improper Neutralization of Input During Web Page Generation known as Cross-site Scripting, and specifically highlights the failure to restrict allowed HTML elements based on context. It also maps to ATT&CK techniques related to Client-Side Injection, where attackers leverage client-side scripting languages like JavaScript to execute malicious commands within a victim's browser environment. The lack of proper input validation against special characters that have meaning in these scripts allows for the successful injection and subsequent execution of arbitrary code.
Mitigation strategies must focus on immediate remediation through software updates and rigorous security hardening practices. Administrators running versions of Kubio AI Page Builder prior to 2.9.3 should upgrade to version 2.9.3 or later, where this logic error has been corrected by properly scoping the allowed HTML elements to the editor context only. Until an update is applied, site administrators can implement temporary workarounds such as disabling public access to draft previews and manually reviewing all submissions with extreme caution using browser security tools that block script execution during review sessions. Additionally, implementing a Web Application Firewall (WAF) with rulesets tuned for cross-site scripting detection can provide an additional layer of defense by intercepting and blocking requests containing suspicious HTML markup before it reaches the application logic. Regular audits of plugin codebases to ensure strict adherence to context-aware sanitization standards are essential to prevent similar vulnerabilities in future updates or other plugins within the ecosystem.