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CVE-2021-28796

CVE-2021-28796: Cross-Site Scripting in Qiita-Markdown

6.1

CVSS Score
3.1

Basic Information

CVE ID
CVE-2021-28796
GHSA ID
GHSA-f2c9-5jqw-3xh3
EPSS Score
0.44333%
CWE
CWE-79
Published
8/2/2021
Updated
9/5/2023
KEV Status
No
Technology
TechnologyRuby

Technical Details

CVSS Vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N
Package NameEcosystemVulnerable VersionsFirst Patched Version
qiita-markdownrubygems< 0.33.00.33.0

Vulnerability Intelligence
Miggo AIMiggo AI

Miggo AIRoot Cause Analysis

The vulnerability stems from improper input sanitization in Markdown transformers handling URI attributes. Commit messages reference XSS fixes in transformers and URI error handling. Advisories specifically mention javascript: URI exploitation in iframes, indicating the vulnerable code paths involve URI processing in embed/image link transformers and script filtering components. The patched version 0.33.0 would have added proper URI scheme validation and sanitization in these transformation layers.

Vulnerable functions

Only Mi**o us*rs **n s** t*is s**tion

WAF Protection Rules

WAF Rule

In*r*m*nts Qiit*-M*rk*own ***or* *.**.* *llows XSS in tr*ns*orm*rs.

Reasoning

T** vuln*r**ility st*ms *rom improp*r input s*nitiz*tion in M*rk*own tr*ns*orm*rs **n*lin* URI *ttri*ut*s. *ommit m*ss***s r***r*n** XSS *ix*s in tr*ns*orm*rs *n* URI *rror **n*lin*. **visori*s sp**i*i**lly m*ntion `j*v*s*ript:` URI *xploit*tion in i