CVE-2021-43409: The “WPO365 | LOGIN” WordPress plugin (up to and including version 15.3) by wpo365.com is vulnerable to a persistent Cross-Site Scripting (XSS) vulner...

Description

The “WPO365 | LOGIN” WordPress plugin (up to and including version 15.3) by wpo365.com is vulnerable to a persistent Cross-Site Scripting (XSS) vulnerability (also known as Stored or Second-Order XSS). Persistent XSS vulnerabilities occur when the application stores and retrieves client supplied data without proper handling of dangerous content. This type of XSS vulnerability is exploited by submitting malicious script content to the application which is then retrieved and executed by other application users. The attacker could exploit this to conduct a range of attacks against users of the affected application such as session hijacking, account take over and accessing sensitive data. In this case, the XSS payload can be submitted by any anonymous user, the payload then renders and executes when a WordPress administrator authenticates and accesses the WordPress Dashboard. The injected payload can carry out actions on behalf of the administrator including adding other administrative users and changing application settings. This flaw could be exploited to ultimately provide full control of the affected system to the attacker.

Metrics

CVSS 3.1

6.1/10

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

EPSS Probability

0.94%

56.3th percentile

Probability of exploitation in the next 30 days. Learn more

Weakness Enumeration

Affected Software

Vendor	Product	Versions
Wpo365	Wordpress \+ Azure Ad \/ Microsoft Office 365	<= 15.3

References

https://appcheck-ng.com/wordpress-microsoft-office-365-azure-ad-login-persistent-cross-site-scripting/Exploit, Third Party Advisory
https://www.wpo365.com/change-log/Release Notes, Vendor Advisory
https://appcheck-ng.com/wordpress-microsoft-office-365-azure-ad-login-persistent-cross-site-scripting/Exploit, Third Party Advisory
https://www.wpo365.com/change-log/Release Notes, Vendor Advisory

Timeline

Published: Nov 19, 2021
Last Modified: Jun 17, 2026
Status: Modified

Frequently Asked Questions

What is CVE-2021-43409?

The “WPO365 | LOGIN” WordPress plugin (up to and including version 15.3) by wpo365.com is vulnerable to a persistent Cross-Site Scripting (XSS) vulnerability (also known as Stored or Second-Order XSS). Persistent XSS vulnerabilities occur when the application stores and retrieves client supplied data without proper handling of dangerous content. This type of XSS vulnerability is exploited by submitting malicious script content to the application which is then retrieved and executed by other application users. The attacker could exploit this to conduct a range of attacks against users of the affected application such as session hijacking, account take over and accessing sensitive data. In this case, the XSS payload can be submitted by any anonymous user, the payload then renders and executes when a WordPress administrator authenticates and accesses the WordPress Dashboard. The injected payload can carry out actions on behalf of the administrator including adding other administrative users and changing application settings. This flaw could be exploited to ultimately provide full control of the affected system to the attacker.

How severe is CVE-2021-43409?

CVE-2021-43409 has a CVSS score of 6.1/10 (MEDIUM severity). The EPSS model estimates a 0.94% probability of exploitation in the next 30 days.

How do I fix CVE-2021-43409?

Check the vendor references and advisories linked above for patched versions and mitigation guidance. You can also run a Strix scan to test if your systems are affected.