CVE-2026-16640 in Search API Autocomplete
Summary
by MITRE • 08/26/2026
Improper Neutralization of Input During Web Page Generation ("Cross-site Scripting") vulnerability in Drupal Search API Autocomplete allows Reflected XSS. This issue affects Search API Autocomplete versions: from 0.0.0 to 1.12.0.
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Analysis
by VulDB Data Team • 08/26/2026
The identified security flaw represents a classic instance of Improper Neutralization of Input During Web Page Generation, commonly known as Cross-Site Scripting or XSS. Specifically, this vulnerability manifests within the Search API Autocomplete module for Drupal, affecting versions ranging from 0.0.0 up to and including version 1.12.0. The core technical deficiency lies in the application's failure to adequately sanitize or encode user-supplied input before it is incorporated into dynamically generated web pages. When a user submits data through an autocomplete field, the system processes this input but fails to apply necessary security filters that would strip out malicious script tags or event handlers. Consequently, if an attacker crafts a specific URL payload containing executable JavaScript code and tricks a victim into accessing it via a search query parameter, the browser interprets the injected scripts as legitimate content from the trusted domain. This reflects directly back in the response without being stored on the server, classifying this strictly as a Reflected XSS vulnerability rather than a Stored one.
From an operational perspective, the impact of this reflected cross-site scripting flaw is significant because it allows for session hijacking and credential theft under specific social engineering conditions. An attacker can construct a malicious link that includes their own JavaScript payload within the search query parameters. When a victim clicks this link while logged into the Drupal site, the browser executes the script in the context of the vulnerable application's domain. This grants the attacker access to sensitive information such as session cookies, authentication tokens, and potentially personally identifiable information displayed on the page. Furthermore, the malicious script can perform actions on behalf of the user without their consent, such as changing account settings, posting content, or initiating financial transactions if applicable. The reflected nature means that each attack requires individual targeting via a crafted link, which limits automated mass exploitation but increases the success rate through targeted phishing campaigns where trust in the domain is already established by the victim.
In terms of industry standard classification, this vulnerability aligns with CWE-79: Improper Neutralization of Input During Web Page Generation Cross-site Scripting. The specific behavior maps to MITRE ATT&CK technique T1059.007, which covers JavaScript execution within a browser environment. Additionally, the vector for delivery often involves social engineering tactics categorized under T1189 Drive-by Compromise or T1204 User Execution, as the victim must actively interact with the malicious link to trigger the code execution. The lack of output encoding is the primary technical root cause, indicating that the development team did not implement robust input validation and context-aware output escaping mechanisms when rendering the autocomplete results back to the client side. This oversight violates fundamental web security principles outlined in OWASP guidelines regarding secure coding practices for dynamic content generation.
To mitigate this vulnerability, immediate action must be taken by upgrading the Search API Autocomplete module to a version newer than 1.12.0, where the developers have presumably implemented proper input sanitization and output encoding techniques. If an upgrade is not immediately feasible due to compatibility constraints with other modules or custom code, administrators should implement compensating controls at the web server level using Web Application Firewalls that can detect and block common XSS payloads in query parameters. Additionally, enabling Content Security Policy headers on the Drupal site can significantly reduce the impact of any successful exploitation by restricting the sources from which scripts are allowed to execute. Developers reviewing similar code paths within their custom modules should ensure that all user inputs are validated against a whitelist of expected characters and that all output is encoded according to its context in HTML, JavaScript, or URL structures to prevent future instances of this class of vulnerability.