WordPressCMS
CVE-2021-39202
Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.
NVD · uneditedWordPress is a free and open-source content management system written in PHP and paired with a MySQL or MariaDB database. In affected versions the widgets editor introduced in WordPress 5.8 beta 1 has improper handling of HTML input in the Custom HTML feature. This leads to stored XSS in the custom HTML widget. This has been patched in WordPress 5.8. It was only present during the testing/beta phase of WordPress 5.8.
Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.
dbcve analysis · high confidenceA stored XSS vulnerability exists in the Custom HTML widget of WordPress 5.8 beta 1 due to improper handling of HTML input in the widgets editor. Attackers can inject malicious scripts that execute when users view pages containing the compromised custom HTML widget.
Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.
Affected products & versions What the vendor confirmedThe version ranges the vendor confirmed as vulnerable. If your version sits inside a range here, treat yourself as exposed until you have upgraded.
NVD · CPE data
WordPressCMS
= 5.8CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.
From the vector- Attack vector
- Network
- Complexity
- Low
- Privileges
- Low
- User interaction
- Required
- Scope
- Changed
- Confidentiality
- Low
- Integrity
- Low
- Availability
- None
CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:L/I:L/A:N
Am I affected? How to checkSteps we derive from the advisory and the affected-version data, so you can decide whether this CVE reaches your setup. They are a guide, not a scan — your own configuration is the authority.
dbcve checksWork through these to decide whether this CVE applies to you.
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Check WordPress versionNavigate to Dashboard > Updates or view wp-includes/version.php to determine the exact installed WordPress versionAffected if The version is exactly 5.8-beta1. This vulnerability existed only in the beta 1 release and was patched in the final WordPress 5.8 release
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Review Custom HTML widgetsGo to Appearance > Widgets and examine all Custom HTML widgets currently active on the siteAffected if Any Custom HTML widget contains unexpected HTML or script tags that you did not intentionally add
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Inspect rendered page sourceView the source of pages containing Custom HTML widgets and search for script tags within widget areasAffected if Malicious script tags appear in the rendered output that correspond to compromised Custom HTML widgets
You are affected only if running WordPress 5.8-beta1 specifically and have unauthorized scripts injected into Custom HTML widgets on your site
Generated from the published advisory. Verify against your own configuration.
Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.
dbcve · scopedUpgrade to WordPress 5.8 or later, as this vulnerability was only present during the beta testing phase and was patched in the final 5.8 release.
WordPress 5.8 (stable) or later
- Identify current WordPress version by checking the WordPress admin dashboard or wp-includes/version.php file
- If running a WordPress 5.8 beta version, upgrade to WordPress 5.8 stable release or later
- Ensure WordPress core is updated to version 5.8 or higher, which contains the patch for this XSS vulnerability in the Custom HTML widget
- After upgrade, verify the Custom HTML widget functions correctly and the XSS vulnerability is resolved
Generated from the published advisory — verify against the referenced sources before acting.
Fix this in WordPress
Scoped from the published advisory
- Consultation1.0 h
- Implementation2.0 h
- Testing2.0 h
- Review / QA1.0 h
An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $1,664.
Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2021-39202 — or any other known-vulnerable package — straight from your lock files. Free and open source; it runs locally and uploads nothing.
References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.
Primary sourcesPractitioner notes
ContributedPeer-ranked notes from engineers who’ve handled CVE-2021-39202 in production — separate from our analysis above.
The advisory tells you what broke. It rarely tells you what actually worked. If you’ve dealt with this one, that detail is what the next engineer is searching for.
- The version that genuinely resolved it — not the one the vendor claimed
- A config change or rule that shut the vector down
- A gotcha in the upgrade path that cost you an afternoon
No notes yet
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A place for practitioners to share what actually worked: a mitigation you’ve tested, a configuration change, a version- or environment-specific caveat, or a link to a verified patch. The most useful notes rise to the top as peers upvote them, so the signal stays high.
- Verified mitigations, workarounds, and config changes
- Version or environment caveats, and links to real fixes
- No weaponised exploit code, or anything meant to cause harm
- No spam, self-promotion, credentials, or personal data