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CVE Record

CVE-2020-7773: Cross-site Scripting (XSS)

This affects the package markdown-it-highlightjs before 3.3.1. It is possible insert malicious JavaScript as a value of lang in the markdown-it-highlightjs Inline code highlighting feature. const markdownItHighlightjs = require("markdown-it-highlightjs"); const md = require('markdown-it'); const reuslt_xss = md() .use(markdownItHighlightjs, { inline: true }) .render('console.log(42){.">js}'); console.log(reuslt_xss);

MediumCVSS 6.5Not KEV-listedUpdated
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Glexia's TakeAutomated analysismoderate

Security readout for executives and security teams

Plain-English summary

CVE-2020-7773 is an XSS flaw in markdown-it-highlightjs before 3.3.1. If an application renders untrusted Markdown using its inline code highlighting feature, a malicious language value can inject JavaScript into the rendered page.

Executive priority

Treat as a moderate-priority web application exposure. Patch promptly where user-generated Markdown is rendered, especially in customer portals, documentation systems, forums, or internal knowledge tools containing sensitive data.

Technical view

The issue is in markdown-it-highlightjs inline highlighting. The lang value for inline code can be handled unsafely, enabling script injection in rendered HTML. The CVSS 3.1 score is 6.5 with network attack vector, low complexity, no privileges, and required user interaction.

Likely exposure

Exposure is most likely in Node.js applications that use markdown-it-highlightjs before 3.3.1 and render user-controlled Markdown with inline highlighting enabled. Applications that do not use this package or do not render untrusted Markdown through that feature are less likely exposed.

Exploitation context

The source bundle does not show active exploitation, and KEV is false. Exploitation requires a victim to view rendered malicious Markdown in a vulnerable application. The main business risk is browser-side data exposure through XSS.

Researcher notes

The evidence identifies a vulnerable package boundary, feature condition, and referenced fix discussion. CWE is not listed in the bundle. No source here confirms weaponized public exploitation or broader affected products beyond markdown-it-highlightjs.

Mitigation direction

  • Upgrade markdown-it-highlightjs to version 3.3.1 or later.
  • Prioritize apps rendering user-submitted Markdown content.
  • If upgrade is delayed, review vendor guidance before relying on compensating controls.
  • Avoid rendering untrusted Markdown through vulnerable inline highlighting paths.

Validation and detection

  • Inventory direct and transitive uses of markdown-it-highlightjs.
  • Confirm deployed versions are 3.3.1 or later.
  • Identify routes rendering user-controlled Markdown with inline highlighting enabled.
  • Review dependency lockfiles and built artifacts for stale vulnerable versions.
Prepared
Confidence
high
Sources
5

Public sources used

Generated from the cited source records. This long-tail analysis has not been individually reviewed by a named human.

Potential ATT&CK relevance

Conservative CVE-to-ATT&CK context

These mappings and lookup hints may be relevant to the vulnerability behavior, CWE, affected product, or exposure path. Glexia-inferred context is not an official MITRE, ATT&CK, CWE, or CVE Program mapping.

ATT&CK lookup starting points

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CVE-2020-7773 mapping review

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Vulnerability profileCVE Program record
Severity
Medium
CVSS
6.5 (3.1)
Known Exploited
No
Published

Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:N/A:N/E:P/RL:O/RC:C

Official CVE source material

CNA and ADP enrichment extracted from CVE v5

These fields come from the CVE record and ADP containers, not from Glexia's Take. They preserve time-varying source decisions such as CISA SSVC, KEV status, CVSS metrics, and provider references.

1CVSS vectors
0Timeline events
0ADP providers
4Source links

CVSS vector scores

1 official score

We collect every scored CVSS vector available in the official CNA and ADP containers. When more than one version is present, the table keeps the source vectors side by side instead of collapsing them into the highest score.

ScoreVersionSeverityVectorExploitImpactSource
6.5CVSS 3.1MediumCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:N/A:N/E:P/RL:O/RC:C2.83.6Primary CVE score

Vulnerability scoring details

Base CVSS 3.1 score

6.5Medium
CVSS 3.1 vector shape for CVE-2020-7773Attack VectorAttack ComplexityPrivileges RequiredUser InteractionScopeConfidentiality ImpactIntegrity ImpactAvailability Impact

Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:N/A:N/E:P/RL:O/RC:C

Attack Vector
NetworkAdjacentLocalPhysical
Attack Complexity
LowHigh
Privileges Required
NoneLowHigh
User Interaction
NoneRequired
Scope
ChangedUnchanged
Confidentiality Impact
HighLowNone
Integrity Impact
HighLowNone
Availability Impact
HighLowNone

Source materials

Affected products

Products and packages named in the record

VendorProductVersion / packageStatus
n/amarkdown-it-highlightjsunspecifiedListed
Weakness

CWE details

No CWE listed

CWE links open Glexia weakness intelligence pages with official CWE context, developer remediation guidance, and related CVE mappings.