CVE-2021-39325

OptinMonster <= 2.6.0 - Reflected Cross-Site Scripting

2021-09-20 18:03

Strategic Overview

Status: Patched in 2.6.1
Affected Plugin: Popup Builder & Popup Maker for WordPress – OptinMonster Email Marketing and Lead Generation
Affected Version: <= 2.6.0
CVSS: 6.1Medium
Weakness type: CWE-79 · Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')
CVE: CVE-2021-39325

View all Popup Builder & Popup Maker for WordPress – OptinMonster Email Marketing and Lead Generation vulnerabilities

At a glance

CVE-2021-39325 is a medium-severity Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting') vulnerability in the Popup Builder & Popup Maker for WordPress WordPress plugin, affecting versions <= 2.6.0. It carries a CVSS score of 6.1 (reachable over the network; low attack complexity). Exploitation requires no authentication. The issue is fixed in version 2.6.1; sites on affected versions should update now. Disclosed September 2021, reported by Mariia Aleksandrova.

Vulnerability Overview

The OptinMonster WordPress plugin is vulnerable to Reflected Cross-Site Scripting due to insufficient input validation in the load_previews function found in the ~/OMAPI/Output.php file which allows attackers to inject arbitrary web scripts, in versions up to and including 2.6.0.

Technical Analysis

The vector marks this flaw as remotely reachable over the network, with low attack complexity — no special timing or configuration is needed, and no privileges on the target site.

CWE-79: Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')

Reaching this weakness in Popup Builder & Popup Maker for WordPress <= 2.6.0 takes a caller who can reach the endpoint. Cross-site scripting happens when input from a request is written into a page without being escaped for the context it lands in, so the browser parses attacker-supplied text as markup or script.

Injected script runs with the privileges of whoever views the affected page, which is how these flaws turn into administrator session theft, silent account creation or persistent backdoors in page content. For Popup Builder & Popup Maker for WordPress the fix is 2.6.1: builds <= 2.6.0 are affected, anything from 2.6.1 onward is not.

Remediation

Update to version 2.6.1, or a newer patched version

How does WordSec protect against this?

The attempt arrives as an ordinary request to Popup Builder & Popup Maker for WordPress: WordSec's web application firewall inspects request payloads before WordPress loads them. None of that substitutes for the fix: Popup Builder & Popup Maker for WordPress 2.6.1 closes this, and updating the plugin is the step that ends it.

Firewall
Alerts

External References

https://www.cve.org/CVERecord?id=CVE-2021-39325 https://www.wordfence.com/threat-intel/vulnerabilities/id/3f39c478-7b64-4afc-8c3f-9409e105954a https://nvd.nist.gov/vuln/detail/CVE-2021-39325

Related records

Same weakness class

6.4CVE-2024-4045: Popup Builder by OptinMonster Stored XSSCVE-2024-4045

Other vulnerabilities in Popup Builder & Popup Maker for WordPress – OptinMonster Email Marketing and Lead Generation

CVSS Vector

6.1

CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N

Base

Attack VectorNetwork
Attack ComplexityLow
Privileges RequiredNone
User InteractionRequired
ScopeChanged
ConfidentialityLow
IntegrityLow
AvailabilityNone

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