CVE-2026-71802 in REBUILD
Summary
by MITRE • 09/09/2026
A stored Cross-Site Scripting (XSS) vulnerability exists in the announcement preview component of REBUILD 4.4.3. Although the announcement content undergoes HTML escaping on the server side, the client-side preview code reverses the escaped entities using jQuery's `html().text()` method and subsequently injects the result into the DOM. An administrator or attacker capable of controlling the announcement content can exploit this vulnerability to execute arbitrary JavaScript code in the browsers of users viewing the affected pages "which may include the dashboard, activity feed, or login page, depending on the announcement's visibility settings.
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Analysis
by VulDB Data Team • 09/09/2026
The identified security flaw represents a classic instance of stored Cross-Site Scripting within the REBUILD application version 4.4.3, specifically targeting its announcement preview functionality. This vulnerability stems from an inconsistent handling of input data between server-side rendering and client-side dynamic content manipulation. While the initial submission of announcement content is subjected to HTML entity escaping on the backend, a subsequent processing step in the JavaScript layer effectively neutralizes this protection. The core technical deficiency lies in the use of jQuery's html() method combined with text extraction logic that reverses previously escaped entities before injecting them back into the Document Object Model. This sequence creates a window where malicious payloads, once stored in the database as seemingly safe escaped strings, are decoded and executed upon retrieval by any user accessing pages where these announcements are rendered.
From an operational perspective, this vulnerability allows for persistent code execution without requiring immediate interaction from the victim beyond viewing specific sections of the application. The impact is particularly severe because it targets high-traffic areas such as dashboards, activity feeds, or even login pages depending on how administrators configure announcement visibility settings. An attacker who gains write access to announcements can embed malicious JavaScript that triggers upon page load for every visitor. This leads to potential session hijacking through cookie theft, credential harvesting via fake input fields injected into the DOM, defacement of user interfaces, or redirection to phishing sites designed to compromise further credentials. The persistence of the payload means that remediation requires not only fixing the code but also purging any existing malicious announcements from the database.
This vulnerability aligns with CWE-79, which categorizes improper neutralization of input during web page generation known as Cross-site Scripting. More specifically, it illustrates a failure in output encoding relative to the context where data is rendered, often referred to as DOM-based XSS when the execution occurs within client-side scripts rather than server-generated HTML directly. In terms of offensive security frameworks, this behavior maps closely to MITRE ATT&CK technique T1059.007, which covers JavaScript execution on web browsers. The attack vector leverages stored persistence (T1486) by embedding the payload in a legitimate data field that is subsequently displayed to multiple users, maximizing the blast radius of the compromise without requiring further exploitation steps from the attacker after initial injection.
Mitigation strategies must address both the immediate technical flaw and broader input validation practices. The primary fix involves removing or correcting the client-side logic that reverses HTML entities before DOM insertion. Developers should ensure that any data retrieved for display is either left in its escaped state if it will be rendered as text, or properly sanitized using a robust library like DOMPurify if it must contain allowed HTML tags. It is critical to avoid using html() with unsanitized dynamic content derived from user input. Additionally, implementing Content Security Policy headers can provide an additional layer of defense by restricting the sources from which scripts are loaded and executed, thereby mitigating the impact even if a bypass occurs. Immediate remediation should include patching the application code and auditing existing announcement records to remove any injected malicious payloads before deploying the fix to production environments.