Cross-Site Scripting (XSS) in xhtml-purifier (CVE-2026-61784)
Summary
Cross-site scripting in xhtml-purifier (CVE-2026-61784). Risk of unauthorized operations or information disclosure. Mitigation: upgrade to 0.4.3 or later.
Original description
The description as published by the source.
xhtml-purifier does not HTML-entity-encode attribute values when serializing its sanitized output. In attributeString() (XHTMLPurifier.js, around line 148) the attribute value is concatenated directly into a double-quoted attribute without encoding. As a result, an attacker-controlled value in any allowed attribute (class, style, title, alt, src, href) can include a double-quote character to break out of the attribute and inject an additional attribute, such as a JavaScript event handler (for example onmouseover or onerror). The injected handler survives sanitization and executes when the output is rendered, which is a sanitizer bypass leading to cross-site scripting. The fix HTML-entity-encodes attribute values before serialization.
Source: NIST National Vulnerability Database NVD GitHub Advisory
Auto-generated summary
Assembled by SecPulse from the source data (CVSS, CWE, affected versions) using templates — no AI involved. Check the original description and references below for exact details.
A vulnerability tracked as CVE-2026-61784 has been found in xhtml-purifier.
Risk of unauthorized operations or information disclosure. CVSS score: 6.1/10.
What to do: upgrade xhtml-purifier to 0.4.3 or later.
If unsure, ask your IT team or search "xhtml-purifier CVE-2026-61784" on the vendor's site.
CVE-2026-61784 (xhtml-purifier) — CWE-79 / CVSS v3 6.1
Attack vector: remote (network-reachable) / unauthenticated
Patched: 0.4.3 — apply immediately
Plan: 1) Audit SBOM/dependencies, 2) Stage→prod upgrade, 3) Add WAF/proxy monitoring on affected endpoints, 4) Hunt IOCs in logs.
Refs: see the GHSA / vendor advisory / patched release linked on this page.
Cross-site scripting (XSS) (CWE-79) exists in xhtml-purifier.
Check the vendor advisory for the affected versions of xhtml-purifier.
Severity: Medium (CVSS 6.1/10). Risk of unauthorized operations or information disclosure.
Update to 0.4.3.
Until the patch is applied: disable the affected feature, apply WAF rules, or restrict access via network ACLs.
Search webserver/proxy logs for unusual request patterns matching this CVE's known IOCs. Run grep -r 'xhtml-purifier' . against your dependency files (package-lock.json, requirements.txt, go.sum) to find affected services.
Response actions
Concrete steps and command examples for SOC/SRE teams to execute in order
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1Identify exposure identify
grep -r 'xhtml-purifier' . | grep -v node_modulesリポジトリと本番環境の依存ファイル (package-lock.json / requirements.txt / go.sum / Gemfile.lock 等) で
xhtml-purifierを grep し、稼働しているサービス・バージョンを把握する。 -
2Apply patch patch
Upgrade xhtml-purifier to 0.4.3ステージング環境で 0.4.3 に上げて回帰テスト → 本番反映。回帰テストはアプリの主要ハッピーパスを含めること。
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3Post-deployment verification verify
Confirm patched version is live in productionパッチ適用後、ステージングで PoC または同等の悪用パターンを再現して脆弱性が閉じたことを確認。本番ではアクセスログ・WAF でアラート再発が無いか継続監視。
Affected packages
References
- web github.com
- web github.com
- web nvd.nist.gov
- web github.com
- web github.com
- web github.com