CVE-2025-23703
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 · uneditedCross-Site Request Forgery (CSRF) vulnerability in cstoltenkamp Free MailClient FMC mailclient allows Stored XSS.This issue affects Free MailClient FMC: from n/a through <= 1.0.
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 Cross-Site Request Forgery (CSRF) vulnerability in Free MailClient FMC allows attackers to craft malicious requests that result in Stored XSS. The application lacks proper CSRF token validation, enabling attackers to inject malicious scripts that persist in the application and execute in other users' browsers.
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
- None
- User interaction
- Required
- Scope
- Changed
- Confidentiality
- Low
- Integrity
- Low
- Availability
- Low
CVSS:3.1/AV:N/AC:L/PR:N/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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Identify the installed applicationDetermine if the system is running Free MailClient FMC by reviewing installed packages, web application directories, or service banners. Check application startup logs or configuration files for product identification.Affected if The application is Free MailClient FMC and handles user mail/forms without version-specific patching available.
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Inspect form submissions for CSRF tokensExamine HTML forms in the web interface (login, compose, settings, contacts) by viewing page source or using browser developer tools. Look for hidden input fields containing token values, or check request headers for anti-CSRF tokens.Affected if Forms lack CSRF token fields or tokens are missing from POST requests for state-changing operations.
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Verify session cookie SameSite attributeCapture an authenticated session cookie (via browser dev tools or proxy) and inspect the Set-Cookie header. Check if the SameSite attribute is set to 'Strict' or 'Lax', or is absent.Affected if SameSite attribute is missing or set to 'None', allowing cookies to be sent in cross-origin requests.
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Test for CSRF-to-Stored XSS chainingSubmit a crafted POST request to forms (such as email compose, signature, or contact fields) containing a script tag in input fields, without including a valid CSRF token. Use a tool like Burp Suite or curl to bypass same-origin restrictions.Affected if The malicious payload is accepted and persists in the application, visible to other users without CSRF token validation.
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Check server-side request validationReview server-side code or proxy logs to confirm whether incoming POST requests validate any CSRF token, unique request identifier, or referrer header before processing state-changing operations.Affected if The server accepts and processes POST requests without validating anti-CSRF mechanisms.
If Free MailClient FMC is running and forms lack CSRF tokens while SameSite cookies are not properly set, the environment is vulnerable to CVE-2025-23703.
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 dataImplement CSRF tokens or unique request identifiers for all state-changing operations (forms, POST requests) and validate these tokens server-side. Additionally, set SameSite attributes on session cookies to prevent cross-origin request transmission.
- Consultation4.0 h
- Implementation8.0 h
- Testing4.0 h
- Review / QA2.0 h
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Free · runs locallyCheck whether your project pulls in CVE-2025-23703 — 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-2025-23703 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
- No spam, self-promotion, credentials, or personal data