CVE-2026-83559 Vulnerability Analysis & Exploit Details

CVE-2026-83559 Vulnerability Summary

CVE-2026-83559: Improper encoding or escaping of output in Apache Wicket. org.apache.wicket.core.util.string.JavaScriptUtils#escapeQuotes() replaces each single quote in its input with a backslash and a single quote, and each double quote with a backslash and a double quote, so that the value can be placed inside a JavaScript string literal. It does not escape the backslash, which is the character that has to be escaped, and escaped first, for the rest of that escaping to hold. A value that already holds a backslash immediately before a quote therefore ends up with two backslashes in front of that quote: the first escapes the second, the quote itself is left unescaped, and it closes the literal. Whatever the value carries after that point is no longer text but JavaScript, and it runs in the application's origin and in the session of the user looking at the page. The method is public, is not deprecated, and its documentation states that its result can be part of a JavaScript call such as an alert; the only limitation it notes concerns JSON values, which need different escaping. An application is affected wherever it calls the method itself and places the result inside a JavaScript string literal, from its own code or from a component of its own or of a third party, and the value it escapes holds data an attacker can influence. There is no further condition, and no component of Wicket has to be involved: the application is using the method for what its documentation offers, and the method does not deliver it. Two components shipped with Wicket Extensions pass a value through the method. org.apache.wicket.extensions.ajax.markup.html.AjaxEditableLabel writes the editor's first error feedback message into a single-quoted JavaScript string literal in the Ajax response, so an application is affected through that component where the message shown for a failed edit holds data an attacker can influence, whether that is the submitted value itself or another variable the application sets on the validation error. A validation message can carry the submitted value, because input is a message variable that every form component supplies for its own validation errors, and the documentation shows overriding a validator's message to include it; none of the message bundles shipped with Wicket interpolates it, so an application that has not written such a message is not affected through this component. org.apache.wicket.extensions.ajax.markup.html.repeater.AjaxListPanel passes the serialized markup tag of an appended component through the method and is not affected: the tag comes from the panel's own markup file, and a quote in any of its attribute values, the component's markup id included, is written as a character reference by the tag serialization and cannot close the literal. This issue affects Apache Wicket: from 8.0.0 through 8.19.0, from 9.0.0 through 9.24.0, from 10.0.0 through 10.11.0. Users of Apache Wicket 7.x or older, which are no longer supported, should upgrade to a supported version. Users are recommended to upgrade to version 8.20.0, 9.25.0 or 10.12.0, which fix the issue.

CVE-2026-83559 References

External References

• https://lists.apache.org/thread.html/77kc85ztkxdpp7wg7cv61c4539j9s1g3

CWE Common Weakness Enumeration

CAPEC Common Attack Pattern Enumeration and Classification

• Cross Zone Scripting CAPEC-104 An attacker is able to cause a victim to load content into their web-browser that bypasses security zone controls and gain access to increased privileges to execute scripting code or other web objects such as unsigned ActiveX controls or applets. This is a privilege elevation attack targeted at zone-based web-browser security.
• User-Controlled Filename CAPEC-73 An attack of this type involves an adversary inserting malicious characters (such as a XSS redirection) into a filename, directly or indirectly that is then used by the target software to generate HTML text or other potentially executable content. Many websites rely on user-generated content and dynamically build resources like files, filenames, and URL links directly from user supplied data. In this attack pattern, the attacker uploads code that can execute in the client browser and/or redirect the client browser to a site that the attacker owns. All XSS attack payload variants can be used to pass and exploit these vulnerabilities.
• Web Server Logs Tampering CAPEC-81 Web Logs Tampering attacks involve an attacker injecting, deleting or otherwise tampering with the contents of web logs typically for the purposes of masking other malicious behavior. Additionally, writing malicious data to log files may target jobs, filters, reports, and other agents that process the logs in an asynchronous attack pattern. This pattern of attack is similar to "Log Injection-Tampering-Forging" except that in this case, the attack is targeting the logs of the web server and not the application.
• AJAX Footprinting CAPEC-85 This attack utilizes the frequent client-server roundtrips in Ajax conversation to scan a system. While Ajax does not open up new vulnerabilities per se, it does optimize them from an attacker point of view. A common first step for an attacker is to footprint the target environment to understand what attacks will work. Since footprinting relies on enumeration, the conversational pattern of rapid, multiple requests and responses that are typical in Ajax applications enable an attacker to look for many vulnerabilities, well-known ports, network locations and so on. The knowledge gained through Ajax fingerprinting can be used to support other attacks, such as XSS.

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