CVE-2026-39780

Executive Summary

CVE-2026-39780 is an unauthenticated Cross-Site Scripting (XSS) vulnerability in the Youzify WordPress plugin affecting all versions up to and including 1.3.7. The flaw allows a remote, unauthenticated attacker to inject arbitrary script into a victim's browser session via a crafted request that requires user interaction (UI:R) to trigger. Successful exploitation can lead to session hijacking, credential theft, and malicious redirection within the context of the vulnerable WordPress site, impacting confidentiality and integrity of the affected web application and its users.

Technical Analysis

Youzify is a WordPress community/social plugin that extends user profiles and community features. CVE-2026-39780 is classified under CWE-79 (Improper Neutralization of Input During Web Page Generation / Cross-Site Scripting) and carries a CVSS 3.1 base score of 7.1 with the vector CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:L.

The score components indicate the following characteristics:

• AV:N (Network) — the vulnerability is exploitable remotely over the network.
• AC:L (Low) — no special conditions beyond normal access are required.
• PR:N (None) — no authentication is required; the attacker does not need a valid account on the target site.
• UI:R (Required) — exploitation depends on a victim performing some action (e.g., visiting a crafted link or interacting with a page).
• S:C (Changed) — the impact scope crosses a security boundary (e.g., from the vulnerable component into the victim's browser context, or into another origin).
• C:L / I:L / A:L — low confidentiality, integrity, and availability impact respectively.

At the class level, unauthenticated reflected or stored XSS in a WordPress plugin typically arises when user-supplied input is rendered into an HTML response without adequate output encoding or sanitization, and without a nonce or capability check gating the affected parameter. The "unauthenticated" designation means the vulnerable code path is reachable without logging in — commonly an AJAX action registered for unauthenticated users, a public-facing shortcode, or a query-string parameter reflected into the page. Because the NVD description does not disclose the exact parameter name, endpoint, or function, the precise injection point cannot be confirmed; no public proof-of-concept or Nuclei template is available to validate the mechanism.

What can be stated with confidence from the data provided:

• The vulnerability is XSS (CWE-79).
• It is unauthenticated (PR:N).
• It requires user interaction (UI:R), consistent with the victim needing to load a crafted URL or page.
• The scope is changed (S:C), meaning the injected script executes in a context that crosses a trust boundary — a classic hallmark of XSS where attacker-controlled script runs in the victim's browser under the vulnerable site's origin.
• The affected product is Youzify, all versions ≤ 1.3.7.

An attacker must convince a victim to visit a crafted URL or interact with a page from the vulnerable site. The script executes with the privileges and origin of the vulnerable site, enabling theft of session cookies (if not HttpOnly), CSRF token exfiltration, credential harvesting via injected forms, or redirection to attacker-controlled infrastructure.

Exploitation Scenarios

No public proof-of-concept is available; the attack chain below is inferred strictly from the vulnerability class (unauthenticated XSS, CWE-79) and the CVSS vector. No specific parameter names, endpoints, or function names are asserted because none are disclosed in the NVD description.

1) Reconnaissance / Target Identification An attacker enumerates internet-facing WordPress sites running the Youzify plugin at version ≤ 1.3.7. This is achievable through passive scanning (e.g., Shodan dorks targeting the plugin directory path or plugin-specific HTML markers) or active fingerprinting of /wp-content/plugins/youzify/ asset paths and plugin version metadata in loaded scripts. Targets of interest are community/social sites with authenticated user populations, where session hijacking yields the most value.

2) Triggering the Flaw Class The attacker crafts a URL or page that delivers a malicious script payload into a vulnerable input that is reflected (or stored) into the HTML response without proper encoding/sanitization. Because the vulnerability is unauthenticated (PR:N), the attacker does not need an account to reach the injection point. Because user interaction is required (UI:R), the attacker must deliver the crafted link to a victim — via phishing email, social engineering, forum/message embedding, or a third-party site — and induce the victim to click it.

3) Payload / Execution (Class-Level) On interaction, the victim's browser requests the vulnerable resource; the response contains the attacker's script inline because the input was not neutralized. The script executes in the origin of the vulnerable Youzify site. At the class level, typical payload objectives include exfiltrating the document cookie or anti-CSRF tokens to an attacker-controlled endpoint, or injecting a fake login form to capture credentials. No specific payload structure is asserted here because the injection context (HTML body, attribute, JavaScript, etc.) is not disclosed.

4) Post-Exploitation Impact Successful script execution in the victim's browser context (Scope:Changed) enables:

• Session hijacking if cookies are not protected with HttpOnly.
• Account takeover via CSRF-token theft or credential phishing.
• Malicious redirection, drive-by download lures, or defacement within the victim's view.
• Chaining with administrative victims (if an admin is lured) to escalate to full site compromise. The rated impact is Low for C/I/A, reflecting that exploitation is not directly destructive to the server but compromises user sessions and page integrity.

No exploit code, PoC, or Nuclei template is publicly tracked, and CISA KEV does not list this CVE as exploited in the wild.

Impact Assessment

CVE-2026-39780 has a CVSS 3.1 base score of 7.1 (High). Business impact analysis by subscore:

• Confidentiality: Low (C:L) — attacker may read limited data from the victim's session, such as cookies or in-page content. The low rating reflects that no server-side database exfiltration is directly enabled by XSS alone, but user-visible data and tokens are at risk.
• Integrity: Low (I:L) — the attacker can modify the content rendered to the victim (e.g., injected forms or scripts), but the underlying stored data is not directly altered.
• Availability: Low (A:L) — no direct denial of service; availability impact is negligible or indirect (e.g., redirection away from the site).
• Scope: Changed (S:C) — the impact crosses a security boundary; script executes in a different security context than the vulnerable component, which is why the score is elevated despite low C/I/A.

Affected Systems: WordPress installations running the Youzify plugin at version ≤ 1.3.7. These are typically community, membership, or social-network sites with user-generated content and authenticated user bases — environments where session theft has outsized value.

Blast Radius: Any visitor (authenticated or not) who can be induced to interact with a crafted link is a potential victim. Sites hosting privileged administrative users are at elevated risk if an admin is targeted, since XSS against an admin session can lead to full site compromise. Because exploitation requires user interaction and there is no known wormable or self-propagating vector, mass compromise is unlikely without a targeted campaign.

Detection Guidance

Sigma Rule

title: Potential Youzify Unauthenticated XSS Exploitation Attempt (CVE-2026-39780)
id: 8b2c1f4e-7a3d-4c9b-9e21-5f6d0a1c3b7e
status: experimental
description: Detects requests to Youzify plugin resources containing common XSS payload markers in query parameters, indicative of exploitation attempts against CVE-2026-39780.
references:
  - https://nvd.nist.gov/vuln/detail/CVE-2026-39780
author: valtersit.com
date: 2026-01-01
logsource:
  category: webserver
  product: apache
detection:
  selection_path:
    cs-uri-stem|contains:
      - '/wp-content/plugins/youzify/'
  selection_payload:
    cs-uri-query|contains:
      - '<script'
      - '%3Cscript'
      - 'onerror='
      - 'onload='
      - 'javascript:'
      - 'document.cookie'
      - 'alert('
  condition: selection_path and selection_payload
falsepositives:
  - Legitimate use of these substrings in benign content
level: medium
tags:
  - attack.t1190
  - cwe.79

YARA Rule

rule CVE_2026_39780_Youzify_XSS
{
    meta:
        description = "Detects common XSS payload markers in HTTP request data targeting Youzify plugin (CVE-2026-39780)"
        author = "valtersit.com"
        reference = "https://nvd.nist.gov/vuln/detail/CVE-2026-39780"
        date = "2026-01-01"
        cve = "CVE-2026-39780"

    strings:
        $p1 = "<script" nocase
        $p2 = "onerror=" nocase
        $p3 = "onload=" nocase
        $p4 = "javascript:" nocase
        $p5 = "document.cookie" nocase
        $p6 = "alert(" nocase
        $plug = "/wp-content/plugins/youzify/" nocase

    condition:
        $plug and any of ($p*)
}

Suricata IDS Rule

alert http any any -> any any (msg:"CVE-2026-39780 Youzify Unauthenticated XSS Exploitation Attempt"; flow:established,to_server; http.uri; content:"/wp-content/plugins/youzify/"; nocase; http.uri; pcre:"/(%3C|<)script|onerror%3D|onerror=|onload%3D|onload=|javascript%3A|javascript:|document%2Ecookie|document\.cookie/i"; classtype:web-application-attack; reference:cve,2026-39780; sid:2026397801; rev:1;)

Elastic Detection

sequence by source.ip with maxspan=5s
  [network where http.request.method == "GET" and
     wildcard(http.request.uri.path, "/wp-content/plugins/youzify/*")]
  [network where wildcard(http.request.uri.query, "*<script*") or
     wildcard(http.request.uri.query, "*onerror=*") or
     wildcard(http.request.uri.query, "*document.cookie*") or
     wildcard(http.request.uri.query, "*javascript:*")]

Splunk SPL Query

index=web sourcetype=access_combined OR sourcetype=nginx:plus:access
uri_path="*/wp-content/plugins/youzify/*"
(uri_query="*<script*" OR uri_query="*%3Cscript*" OR uri_query="*onerror=*" OR uri_query="*onload=*" OR uri_query="*javascript:*" OR uri_query="*document.cookie*")
| stats count min(_time) as first_seen max(_time) as last_seen values(uri_query) as payloads by src_ip, uri_path
| sort - count
| convert ctime(first_seen) ctime(last_seen)

Wazuh OSSEC Rule

<group name="web,appsec,youzify,">
  <rule id="100780" level="10">
    <decoded_as>json</decoded_as>
    <field name="url">/wp-content/plugins/youzify/</field>
    <regex field="url" type="pcre2">(?i)(%3C|<)script|onerror(%3D|=)|onload(%3D|=)|javascript(:|%3A)|document(%2E|\.)cookie</regex>
    <description>CVE-2026-39780: Potential Youzify unauthenticated XSS exploitation attempt detected in HTTP request</description>
    <mitre>
      <id>T1190</id>
    </mitre>
    <group>cve_2026_39780,xss,</group>
  </rule>
</group>

Mitigation & Patch Guidance

Patch confidence: 0/4 — UNPATCHED. No patch evidence exists from any tracked source, and no workaround is documented.

1) Immediate Mitigations (no official fix available)

• Deploy a Web Application Firewall (WAF) with virtual patching rules that block XSS payload patterns in requests to Youzify plugin paths (see detection rules above for candidate signatures).
• Enforce Content Security Policy (CSP) headers with script-src 'self' and avoid unsafe-inline to reduce XSS execution impact.
• Ensure session cookies are set with HttpOnly, Secure, and SameSite attributes to blunt session theft.
• If Youzify is not business-critical, disable or remove the plugin until a fixed version is released.
• Restrict plugin exposure by limiting access to /wp-content/plugins/youzify/ where operationally feasible.

2) Patch / Upgrade Steps

• No patched version is available. Monitor the plugin vendor (Youzify) and the WordPress plugin repository for a security release addressing CVE-2026-39780.
• Once a fixed version is published, upgrade immediately and verify the plugin version in the WordPress admin dashboard.
• Because there is no vendor fix, maintain compensating controls (WAF virtual patching, CSP) in the interim.

3) Long-Term Hardening

• Implement a vulnerability management program that tracks WordPress plugins against CVE feeds and removes abandoned or unmaintained plugins.
• Adopt WAF virtual patching as a standard compensating control for unpatched third-party components.
• Enforce least-privilege and strong authentication for WordPress admin accounts; deploy MFA to reduce XSS-to-account-takeover chains.
• Adopt a strict Content Security Policy for all WordPress sites and validate it regularly.
• Conduct periodic security reviews of installed community/social plugins that render user-supplied data.

References

• NVD — CVE-2026-39780: https://nvd.nist.gov/vuln/detail/CVE-2026-39780
• CWE-79 — Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting'): https://cwe.mitre.org/data/definitions/79.html
• CVSS 3.1 Specification: https://www.first.org/cvss/v3.1/specification-document
• MITRE ATT&CK T1190 — Exploit Public-Facing Application: https://attack.mitre.org/techniques/T1190/
• WordPress Plugin Security — Youzify plugin page (monitor for security release): https://wordpress.org/plugins/youzify/

No known threat actor campaigns or exploit-in-the-wild evidence have been associated with CVE-2026-39780. The CVE is not listed in CISA KEV, and no public PoC, exploit code, or Nuclei template is available. EPSS has not yet assigned a score.