How severe is CVE-2021-39357?

CVE-2021-39357 has a CVSS 3.x base score of 5.5, rated medium severity. It is exploitable over network with low attack complexity, requires high privileges and no user interaction. Impact on confidentiality is low, integrity low, and availability none.

Is CVE-2021-39357 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 1% (55th percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2021-39357?

CVE-2021-39357 affects Zeen101 Leaky Paywall. See the affected-products list for the exact vulnerable versions.

How do I fix CVE-2021-39357?

Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround.

When was CVE-2021-39357 published?

CVE-2021-39357 was published on 2021-10-21 and last updated on 2026-06-17.

CVE-2021-39357

CVE-2021-39357 is a medium-severity vulnerability in Zeen101 Leaky Paywall with a CVSS 3.x base score of 5.5. 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

Severity: Medium (CVSS 3.x base score 5.5)
CVSS v2: 3.5
EPSS exploit prediction: 1% (55th percentile)
Actively exploited: Not listed in CISA KEV
Weakness: CWE-79
Affected product: Zeen101 Leaky Paywall
Published: 2021-10-21
Last modified: 2026-06-17

Description

The Leaky Paywall WordPress plugin is vulnerable to Stored Cross-Site Scripting due to insufficient input validation and sanitization via the ~/class.php file which allowed attackers with administrative user access to inject arbitrary web scripts, in versions up to and including 4.16.5. This affects multi-site installations where unfiltered_html is disabled for administrators, and sites where unfiltered_html is disabled.

Frequently asked questions

What is CVE-2021-39357?: The Leaky Paywall WordPress plugin is vulnerable to Stored Cross-Site Scripting due to insufficient input validation and sanitization via the ~/class.php file which allowed attackers with administrative user access to inject arbitrary web scripts, in versions up to and including 4.16.5. This affects multi-site installations where unfiltered_html is disabled for administrators, and sites where unfiltered_html is disabled.
How severe is CVE-2021-39357?: CVE-2021-39357 has a CVSS 3.x base score of 5.5, rated medium severity. It is exploitable over network with low attack complexity, requires high privileges and no user interaction. Impact on confidentiality is low, integrity low, and availability none.
Is CVE-2021-39357 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 1% (55th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2021-39357?: CVE-2021-39357 affects Zeen101 Leaky Paywall. See the affected-products list for the exact vulnerable versions.
How do I fix CVE-2021-39357?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround.
When was CVE-2021-39357 published?: CVE-2021-39357 was published on 2021-10-21 and last updated on 2026-06-17.

References

Affected products (1)

cpe:2.3:a:zeen101:leaky_paywall:*:*:*:*:*:wordpress:*:*

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