CVE-2026-39693
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 · uneditedImproper Neutralization of Input During Web Page Generation ('Cross-site Scripting') vulnerability in fesomia FSM Custom Featured Image Caption fsm-custom-featured-image-caption allows DOM-Based XSS.This issue affects FSM Custom Featured Image Caption: from n/a through <= 1.25.1.
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 · moderate confidenceA DOM-Based Cross-Site Scripting (XSS) vulnerability exists in the fsm-custom-featured-image-caption WordPress plugin. The vulnerability allows attackers to inject malicious JavaScript code through the featured image caption functionality, which is then executed in victims' browsers when they view affected pages. This occurs due to improper neutralization of user-supplied input during client-side DOM manipulation.
Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.
CVSS 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
- High
- User interaction
- Required
- Scope
- Changed
- Confidentiality
- Low
- Integrity
- Low
- Availability
- Low
CVSS:3.1/AV:N/AC:L/PR:H/UI:R/S:C/C:L/I:L/A:L
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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Confirm plugin installation and activation statusIn WordPress admin, navigate to Plugins > Installed Plugins and look for 'FSM Custom Featured Image Caption' or 'fesomia FSM Custom Featured Image Caption'. Check if it is currently activated.Affected if The plugin is installed and activated on the WordPress site.
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Identify installed plugin versionClick on the plugin name in the Plugins list to view its details, or inspect the plugin's main PHP file header for the 'Version' field. Compare the version number to 1.25.1.Affected if The installed version is 1.25.1 or lower.
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Determine if custom featured image captions are in useGo to Posts or Pages in the WordPress admin. Edit a post and check if a custom featured image caption field (provided by this plugin) is present and populated for any published content.Affected if The plugin has custom featured image captions configured on any published posts or pages.
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Inspect browser DOM for unsanitized output renderingView a page with a featured image caption on the frontend. Right-click > Inspect Element. Locate the caption in the HTML and check if the caption text appears to be inserted directly into innerHTML or similar DOM methods without visible encoding (look for unescaped HTML characters like <, >, or quotes).Affected if The caption content renders as raw HTML or unescaped characters in the page source.
A site is affected if the FSM Custom Featured Image Caption plugin (version 1.25.1 or lower) is active and has custom featured image captions configured, which could allow malicious script injection through unsanitized input in the DOM.
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.
From vendor dataUpdate the FSM Custom Featured Image Caption plugin to the latest version which includes proper input sanitization and output encoding for the caption field to prevent XSS execution. Until a patch is available, disable the plugin or restrict access to trusted users only.
- Consultation2.0 h
- Implementation3.0 h
- Testing2.0 h
- Review / QA1.0 h
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Free · runs locallyCheck whether your project pulls in CVE-2026-39693 — 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-2026-39693 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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- 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
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