CVE-2020-8923
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 · uneditedAn improper HTML sanitization in Dart versions up to and including 2.7.1 and dev versions 2.8.0-dev.16.0, allows an attacker leveraging DOM Clobbering techniques to skip the sanitization and inject custom html/javascript (XSS). Mitigation: update your Dart SDK to 2.7.2, and 2.8.0-dev.17.0 for the dev version. If you cannot update, we recommend you review the way you use the affected APIs, and pay special attention to cases where user-provided data is used to populate DOM nodes. Consider using Element.innerText or Node.text to populate DOM elements.
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 confidenceA DOM Clobbering bypass in Dart's HTML sanitization library allows attackers to inject arbitrary HTML/JavaScript (XSS) by exploiting how the sanitizer handles certain HTML element attributes that can overwrite DOM properties, bypassing the sanitization checks.
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< 2.7.2= 2.8.0CVSS 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 the installed Dart SDK versionRun 'dart --version' in your terminal or check the version in your pubspec.lock file under the sdk dependencyAffected if The version is below 2.7.2 or is exactly 2.8.0
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Locate Dart code that uses HTML sanitizationSearch your codebase for imports of 'package:html' or 'dart:html', and look for usage of the sanitizer class or html methodsAffected if Your project imports and uses Dart's HTML sanitization library
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Check if innerHTML is used for DOM manipulationSearch your Dart code for instances of .innerHTML being assigned user-controlled or untrusted dataAffected if innerHTML is used to render content that originates from untrusted sources
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Verify the sanitizer is applied before innerHTML assignmentExamine the code flow where innerHTML is populated; determine if the HtmlEscape or sanitizer methods process the data firstAffected if The code relies solely on Dart's built-in HTML sanitization without additional escaping
You are affected if your environment runs Dart SDK version 2.7.1 or earlier, or exactly 2.8.0, AND your code uses Dart's HTML sanitization library with innerHTML to render untrusted content.
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 data2.7.2
Update Dart SDK to version 2.7.2 (stable) or 2.8.0-dev.17.0 (dev). If updating is not feasible, refactor code to use Element.innerText or Node.text instead of innerHTML for DOM population.
- Consultation2.0 h
- Implementation8.0 h
- Testing4.0 h
- Review / QA2.0 h
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Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2020-8923 — 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-2020-8923 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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- Version or environment caveats, and links to real fixes
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