CVE-2026-57728 in Flatsome Plugin
Summary
by MITRE • 07/13/2026
Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting') vulnerability in UX-themes Flatsome flatsome allows Reflected XSS.This issue affects Flatsome: from n/a through <= 3.20.5.
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Analysis
by VulDB Data Team • 07/13/2026
Cross-site scripting vulnerabilities represent one of the most prevalent and dangerous web application security flaws, with reflected xss attacks specifically targeting user input that gets immediately reflected back to the browser without proper sanitization. The vulnerability in UX-themes Flatsome flatsome version 3.20.5 and earlier allows attackers to inject malicious scripts into web pages viewed by other users through manipulated input parameters. This particular flaw exists within the web page generation process where user-supplied data is not properly neutralized before being rendered back to the browser, creating an opportunity for attackers to execute arbitrary javascript code in the context of the victim's browser session.
The technical exploitation of this reflected xss vulnerability occurs when a malicious user crafts a specially crafted url containing script payloads that get executed when the vulnerable page processes the input and reflects it back to the user. This type of attack typically involves injecting javascript code through parameters such as search queries, form fields, or url parameters that are not properly validated or escaped before being included in the dynamic web content. The vulnerability falls under the common weakness enumeration category CWE-79 which specifically addresses improper neutralization of input during web page generation, making it a direct implementation of this well-known security pattern. Attackers can leverage this flaw to steal session cookies, perform unauthorized actions on behalf of users, redirect them to malicious sites, or even deface the website with malicious content.
The operational impact of this reflected xss vulnerability in Flatsome presents significant risks to both website administrators and end-users. Website visitors who click on malicious links could have their browser sessions hijacked, leading to potential unauthorized access to user accounts, data theft, or manipulation of website content. The attack surface is particularly concerning given that the vulnerability affects a widely used wordpress theme, meaning numerous websites utilizing Flatsome could be compromised simultaneously. From an att&ck framework perspective, this vulnerability maps directly to technique t1531 which involves tampering with applications and t1059 which covers command and scripting interpreter. The reflected nature of the attack means that the malicious payload doesn't require persistent storage on the server, making detection more challenging for traditional security monitoring systems.
Mitigation strategies for this reflected xss vulnerability in Flatsome should include immediate patching to version 3.20.6 or later where the issue has been resolved through proper input validation and output encoding mechanisms. Organizations should implement comprehensive input sanitization processes that properly escape special characters before rendering user-supplied content in web pages, following established security practices such as those recommended in the owasp top ten project. Additionally, implementing a content security policy (csp) header can provide an additional layer of protection by restricting the sources from which scripts can be loaded and executed. Regular security assessments should include scanning for xss vulnerabilities in all web applications and themes, with particular attention to user input handling mechanisms. The vulnerability also highlights the importance of keeping third-party plugins and themes updated, as outdated components represent common attack vectors that can compromise entire website infrastructures. Security teams should establish monitoring procedures to detect unusual traffic patterns or attempts to exploit known xss vulnerabilities, while also implementing proper logging and alerting mechanisms to quickly identify potential exploitation attempts.