CVE-2025-53631
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 · uneditedflaskBlog is a blog app built with Flask. In versions 2.8.1 and prior, improper sanitization of postContent when submitting POST requests to /createpost leads to arbitrary JavaScript execution (XSS) on all pages the post is reflected on including /, /post/[ID], /admin/posts, and /user/[ID] of the user that made the post. At time of publication, there are no public patches available.
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 confidenceFlaskBlog versions 2.8.1 and prior fail to sanitize user-supplied postContent in POST requests to /createpost, allowing injection of arbitrary JavaScript that executes on all pages where the post is rendered (/, /post/[ID], /admin/posts, /user/[ID]).
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<= 2.8.1CVSS 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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Identify installed FlaskBlog versionCheck the version by examining the package metadata: run `pip show flaskblog` or look for a VERSION file, or check the __init__.py or setup.py for a version attribute. Compare the version number to the affected range.Affected if The installed version is 2.8.1 or lower.
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Verify /createpost endpoint is enabledLocate the route definitions in the application (typically routes.py or app.py) and confirm that the /createpost endpoint exists and accepts POST requests with a postContent parameter.Affected if The /createpost endpoint exists and processes the postContent parameter without sanitization.
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Inspect the post creation handler for input sanitizationExamine the handler function for /createpost in the source code. Look for uses of sanitization libraries such as bleach or markupsafe, or any input validation applied to the postContent field before storing it.Affected if The handler does NOT use input sanitization (bleach, markupsafe, or similar) on the postContent parameter before storage.
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Examine post rendering templates for output encodingReview the template files that render post content on the affected endpoints (/, /post/[ID], /admin/posts, /user/[ID]). Check for proper escaping mechanisms such as Jinja2's |e filter, |escape, or use of bleach in the template.Affected if Templates render post content WITHOUT context-aware escaping (no |e filter, no markupsafe, no bleach) on any of the affected endpoints.
You are affected if your FlaskBlog version is 2.8.1 or lower AND the application stores postContent without sanitization AND renders posts without output encoding on any of the listed endpoints.
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 server-side input validation and output encoding: sanitize all user-provided content using a library like bleach or markupsafe before storage, and apply context-aware escaping when rendering posts on all affected endpoints.
- Consultation3.0 h
- Implementation6.0 h
- Testing3.0 h
- Review / QA2.0 h
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Free · runs locallyCheck whether your project pulls in CVE-2025-53631 — 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-2025-53631 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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