CVE-2021-43409

CVE-2021-43409 is a critical-severity vulnerability in Wpo365 Wordpress + Azure Ad / Microsoft Office 365 with a CVSS 3.x base score of 9.3. It is not currently listed as actively exploited by CISA, and its EPSS exploit-prediction score is low. The underlying weakness is classified as CWE-79.

Key facts

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.

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 3.x base score of 9.3, rated critical severity. It is exploitable over network with low attack complexity, requires no privileges and user interaction. Impact on confidentiality is high, integrity high, and availability none.
Is CVE-2021-43409 being actively exploited?
It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 1% (57th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2021-43409?
CVE-2021-43409 affects Wpo365 Wordpress + Azure Ad / Microsoft Office 365. See the affected-products list for the exact vulnerable versions.
How do I fix CVE-2021-43409?
Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its critical severity, prioritise patching exposed systems.
When was CVE-2021-43409 published?
CVE-2021-43409 was published on 2021-11-19 and last updated on 2026-06-17.

References

Affected products (1)

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