Cross-Site Scripting (XSS) in appium-mcp (CVE-2026-58500)
Summary
Cross-site scripting in appium-mcp (CVE-2026-58500). Data can be tampered with by attackers. Exploitable via createLocatorGeneratorUI. Mitigation: upgrade to 1.85.10 or later.
Original description
The description as published by the source.
Unescaped Locator Data XSS in MCP-UI Resource (createLocatorGeneratorUI)
Summary
appium-mcp's createLocatorGeneratorUI function interpolates attacker-controlled element attributes — text, content-desc, resource-id, and locator selector values — directly into an HTML template literal without any HTML or JavaScript context escaping. An attacker who controls the UI of the app under test can inject arbitrary HTML and JavaScript into the MCP UI resource returned by the generate_locators tool. When a victim's MCP client renders this resource, the injected script executes and can invoke arbitrary MCP tools via window.parent.postMessage, leading to unauthorized MCP tool execution such as taking screenshots, reading page source, or any other registered capability.
Details
The vulnerability is a stored/reflected cross-site scripting (XSS) issue in the MCP UI generation pipeline.
Vulnerable sink — src/ui/mcp-ui-utils.ts:730–740:
${element.text ? `Text: ${element.text}` : ''}
${element.contentDesc ? `Content Desc: ${element.contentDesc}` : ''}
${element.resourceId ? `Resource ID: ${element.resourceId}` : ''}
${selector}
Test
None of element.text, element.contentDesc, element.resourceId, selector, or strategy are HTML-escaped before insertion. The onclick attribute additionally embeds selector and strategy into an inline JavaScript string using only a backtick-escape that is insufficient to prevent breakout via HTML event att…
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-2026-58500 has been found in appium-mcp.
Attackers can target a specific entry point like createLocatorGeneratorUI over the network to misuse the product.
Data can be tampered with by attackers. CVSS score: 8.2/10.
What to do: upgrade appium-mcp to 1.85.10 or later.
If unsure, ask your IT team or search "appium-mcp CVE-2026-58500" on the vendor's site.
CVE-2026-58500 (appium-mcp) — CWE-79 / CVSS v3 8.2
Attack vector: remote (network-reachable) / unauthenticated
Attack surface: createLocatorGeneratorUI / text / generate_locators / window.parent.postMessage
Patched: 1.85.10 — 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 appium-mcp. Attackers reach the vulnerable code path via createLocatorGeneratorUI without authentication.
Check the vendor advisory for the affected versions of appium-mcp. Attack surface: createLocatorGeneratorUI / text / generate_locators / window.parent.postMessage.
Severity: High (CVSS 8.2/10). Data can be tampered with by attackers.
Update to 1.85.10.
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 'appium-mcp' . 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
-
1Identify exposure identify
grep -r 'appium-mcp' . | 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
appium-mcp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 appium-mcp to 1.85.10ステージング環境で 1.85.10 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。
-
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
- package github.com
- web github.com
- web github.com
- web github.com