CVE-2021-39357: The Leaky Paywall WordPress plugin is vulnerable to Stored Cross-Site Scripting due to insufficient input vali

Q: How do I fix CVE-2021-39357?

leaky paywall: upgrade to newer than 4.16.5. Exact commands for each OS are on this page.

Q: Is CVE-2021-39357 being exploited?

CVE-2021-39357 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

Q: What does CVE-2021-39357 affect?

CVE-2021-39357 affects leaky paywall. Severity is medium (CVSS 5.5). 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 s

Q: How urgent is CVE-2021-39357?

Priority 39/100. Public exploit reference

Routine

MEDIUM 5.5UPGRADE

CVE-2021-39357 is a medium-severity flaw (CVSS 5.5) affecting leaky paywall. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

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.

Why this priority

Public exploit reference

A fixed release or distro patch exists.

Risk facts

CVSS score	5.5 (Medium)
Attack vector	Network (remote)
Attack complexity	Low
Privileges needed	High
User interaction	None
EPSS exploit chance	0.9% (top 40%)
CISA exploited list	No
Weakness	CWE-79
Published	2021-10-21
Last modified	2026-06-17

Publisher (CNA): Wordfence · Vendor: zeen101

Last updated 2026-06-17 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Am I affected?

Timeline

2021-10-21 20:15 UTCPublished CVE record published
2026-06-17 04:03 UTCUpdated Record last modified

zeen101 leaky paywall UPGRADE

Affected: <= 4.16.5

Fixed in: newer than 4.16.5

Safe to downgrade to: no unaffected older release

1. Check installed version

apt-cache policy leaky-paywall || rpm -q leaky-paywall || leaky-paywall --version

2. UPGRADE to newer than 4.16.5 (Debian / Ubuntu)

sudo apt update && sudo apt install --only-upgrade leaky-paywall

2. UPGRADE (RHEL / Amazon Linux / Fedora)

sudo dnf upgrade leaky-paywall

Note

Distros often backport fixes without changing the version number. Confirm with the distro advisory or changelog.

Verify at the official source NVD · CVE Program · Report a problem with this page
Scores and fixes here are computed automatically from those and other public sources. Confirm with the vendor advisory before changing production systems.

Quick answers

How do I fix CVE-2021-39357?

leaky paywall: upgrade to newer than 4.16.5. Exact commands for each OS are on this page.

Is CVE-2021-39357 being exploited?

CVE-2021-39357 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

What does CVE-2021-39357 affect?

CVE-2021-39357 affects leaky paywall. Severity is medium (CVSS 5.5). 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 s

How urgent is CVE-2021-39357?

Priority 39/100. Public exploit reference

Software pages

WordPress vulnerabilities · PHP vulnerabilities

References

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