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PostizApplication · Gitroom

CVE-2026-42556

CRITICAL · 9.0 CVSS v3.1 Published 2026-05-08
Mitigation only
No fix yet — a mitigation exists. There is no fixed release. A documented workaround reduces exposure in the meantime.
See remediation →
94/100
Remediation priority · Urgent
Remotely reachable

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 · unedited
Postiz is an AI social media scheduling tool. From version 2.21.6 to before version 2.21.7, any authenticated user who can create a post can store arbitrary HTML in post content by tampering their own save request and send the public preview link /p/<postId>?share=true to another user. The preview page renders that stored HTML with dangerouslySetInnerHTML on the main application origin. This issue has been patched in version 2.21.7.

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 confidence

Stored XSS vulnerability in Postiz allows authenticated users to inject arbitrary HTML by tampering post save requests. When the public preview link (/p/<postId>?share=true) is accessed, the stored HTML is rendered using React's dangerouslySetInnerHTML on the main application origin, enabling execution of malicious scripts in victim browsers.

MitigationUpgrade Postiz to version 2.21.7 or later to apply the patch that properly sanitizes HTML content before rendering in the preview page.

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
PostizApplication
Affected:= 2.21.6

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
Low
User interaction
Required
Scope
Changed
Confidentiality
High
Integrity
High
Availability
High

CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:H/I:H/A:H

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 checks

Work through these to decide whether this CVE applies to you.

  1. Check installed Postiz version
    Locate the package.json or version file in the Postiz installation directory and verify the version number equals 2.21.6
    Affected if Version is exactly 2.21.6
  2. Identify posts with custom HTML content
    Query the posts database table for entries where the content field contains HTML tags such as <script>, <iframe>, <img onerror>, or other HTML markup that was not authored through the normal editor interface
    Affected if Any posts contain raw HTML tags or suspicious markup that could indicate injection
  3. Verify public preview endpoint accessibility
    Attempt to access the /p/<postId>?share=true endpoint for any published post and confirm it renders content without server-side sanitization
    Affected if The public preview link renders post content using React's dangerouslySetInnerHTML without sanitization
  4. Review for unauthorized access to preview links
    Check server access logs for requests to /p/*?share=true URLs that originate from unexpected IP addresses or unauthenticated sessions
    Affected if Public preview links have been accessed by unauthenticated users or from unexpected sources

You are affected if running Postiz version 2.21.6 AND the public preview feature is accessible, allowing any authenticated user to inject and execute arbitrary HTML through stored XSS in post content rendered via the /p/<postId>?share=true endpoint.

Generated from the published advisory. Verify against your own configuration.

Check your environment

Paste your version and any relevant configuration and it will be compared against the affected criteria above. Do not include secrets or credentials.

AI-assisted, checked against the advisory. Informational, not a guarantee.

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 · scoped
Mitigation available No clean upgrade yet — mitigate in the meantime
Mitigation

Upgrade Postiz to version 2.21.7 or later to apply the patch that properly sanitizes HTML content before rendering in the preview page.

Recommended fix High confidence

Postiz version 2.21.7

  1. Upgrade Postiz to version 2.21.7 or later by updating your installation
  2. After upgrading, verify the version is correct by checking the Postiz admin panel or version command
  3. Test that the XSS vulnerability is remediated by creating a post with HTML/script content and confirming the public preview link /p/<postId>?share=true no longer executes the injected code

Generated from the published advisory — verify against the referenced sources before acting.

Fix this in Postiz Scoped from the published advisory
  • Consultation2.0 h
  • Implementation2.0 h
  • Testing2.0 h
  • Review / QA1.0 h
7.0 hours of engineering $1,240
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References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.

Primary sources

Practitioner notes

Contributed

Peer-ranked notes from engineers who’ve handled CVE-2026-42556 in production — separate from our analysis above.

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What this is

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.

What belongs here
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  • Version or environment caveats, and links to real fixes
  • No weaponised exploit code, or anything meant to cause harm
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