CVE-2023-28784 in Contest Gallery Plugin
Summary
by MITRE • 06/22/2023
Unauth. Reflected Cross-Site Scripting (XSS) vulnerability in Contest Gallery plugin <= 21.1.2 versions.
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Analysis
by VulDB Data Team • 09/02/2026
The identified security flaw represents a classic Unauthenticated Reflected Cross-Site Scripting vulnerability within the Contest Gallery WordPress plugin, specifically affecting versions 21.1.2 and earlier. This type of vulnerability arises when an application includes untrusted data in its immediate output without performing adequate validation or encoding. In this specific context, the plugin fails to properly sanitize user-supplied input that is reflected back to the browser within HTTP responses. The lack of proper sanitization allows attackers to inject malicious scripts into web pages viewed by other users, exploiting the trust that a legitimate website has in its own content and the browsers used by visitors.
From a technical perspective, the vulnerability likely stems from insufficient filtering mechanisms applied to query parameters or form inputs before they are rendered on the page. When an attacker crafts a specially designed URL containing malicious JavaScript code as part of the input data, the server processes this request and reflects the payload back in the HTML response without neutralizing special characters such as angle brackets, quotes, or ampersands. Consequently, when a victim clicks the malicious link or visits the crafted page, their browser interprets the injected script as legitimate content from the trusted domain. This execution context is critical because it allows the script to access cookies, session tokens, and other sensitive information stored by the browser for that specific site, effectively bypassing same-origin policy protections intended to isolate web applications.
The operational impact of this vulnerability extends beyond simple defacement or visual manipulation. An attacker can leverage reflected XSS to perform account hijacking by stealing administrative credentials or user sessions through cookie theft. Furthermore, the malicious script can be used to redirect users to phishing sites designed to harvest login information, load malware onto the victim's system via drive-by downloads, or manipulate page content to deceive users into performing unintended actions such as transferring funds or changing settings. Since this vulnerability is unauthenticated, it requires no prior access or valid credentials to exploit, making it particularly dangerous and easy for automated scanning tools and opportunistic attackers to discover and abuse on a large scale.
This flaw aligns with Common Weakness Enumeration identifier CWE-79, which describes Improper Neutralization of Input During Web Page Generation commonly known as Cross-site Scripting. The attack vector corresponds to the ATT&CK technique T1059, specifically sub-technique 007 for JavaScript execution within a browser environment. It also relates to MITRE ATT&CK tactic TA0001 Initial Access if used in phishing campaigns or TA0006 Credential Access if employed to steal session tokens. The unauthenticated nature of the exploit places it high on the risk priority list, as it lowers the barrier for entry significantly compared to authenticated vulnerabilities that require privilege escalation steps first.
To mitigate this vulnerability, immediate action is required by updating the Contest Gallery plugin to version 21.1.3 or later where the issue has been resolved through proper input validation and output encoding practices. Developers should implement strict allow-listing of permitted characters for all user inputs and ensure that any data reflected in HTML responses is encoded using context-appropriate methods such as HTML entity encoding for body content, JavaScript string escaping for script blocks, and URL encoding for query parameters. Additionally, deploying a Web Application Firewall can provide an additional layer of defense by detecting and blocking common XSS payloads before they reach the application logic. Regular security audits and static code analysis tools should be integrated into the development lifecycle to identify similar sanitization oversights in future releases.