CVE-2021-20812
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 scripting vulnerability in Setting screen of Server Sync of Movable Type (Movable Type Advanced 7 r.4903 and earlier (Movable Type Advanced 7 Series) and Movable Type Premium Advanced 1.44 and earlier) allows remote attackers to inject arbitrary script or HTML via unspecified vectors.
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 confidenceCross-site scripting (XSS) vulnerability in the Server Sync Settings screen of Movable Type allows remote attackers to inject arbitrary JavaScript or HTML through unspecified vectors. The vulnerability stems from insufficient input sanitization or output encoding in the settings interface.
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<= 1.44>= 7.0, < 7.8.0CVSS 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
- None
CVSS:3.1/AV:N/AC:L/PR:N/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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Identify Movable Type versionAccess the Movable Type admin dashboard and navigate to the System Overview or Help > About section to view the installed version number.Affected if The version is <= 1.44 OR >= 7.0 and < 7.8.0
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Locate Server Sync Settings screenIn the Movable Type admin panel, navigate to the Server Sync Settings interface (typically found under System Settings, Plugins, or Cloud/Enterprise settings depending on the version).Affected if The Server Sync Settings screen is present and accessible in the admin interface
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Verify Server Sync configuration existsCheck if the Server Sync feature has been configured or enabled by examining the settings fields in the Server Sync Settings screen.Affected if The Server Sync Settings screen displays configurable fields where user input could be injected
Environment is affected if running Movable Type version <= 1.44 or >= 7.0 to < 7.8.0 AND the Server Sync Settings screen is accessible with input fields that lack proper encoding.
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 · scoped7.8.0
Apply proper input validation and output encoding on all user-controllable fields in the Server Sync settings screen. Upgrade to Movable Type Advanced 7 r.4904 or later / Movable Type Premium Advanced 1.45 or later.
Movable Type 7.8.0 (for 7.x series); version after 1.44 (for Premium Advanced)
- Upgrade Movable Type 7.x to version 7.8.0 or later
- For Movable Type Premium Advanced, upgrade to a version after 1.44
- After upgrading, verify the Server Sync settings screen is functioning correctly
- Test that the XSS vulnerability is no longer present in the Setting screen of Server Sync
Generated from the published advisory — verify against the referenced sources before acting.
- Consultation4.0 h
- Implementation8.0 h
- Testing6.0 h
- Review / QA4.0 h
An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $6,176.
Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2021-20812 — 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-2021-20812 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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