CVE-2026-58500 MCP Appium: Unescaped Locator Data XSS in MCP-UI Resource (createLocatorGeneratorUI)
Attackers can inject scripts via mobile app UI attributes, leading to arbitrary JavaScript execution and unauthorized MCP tool invocation in the Appium MCP server.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- A user has to click or open something
- Fix
- None listed
What is CVE-2026-58500?
CVE-2026-58500 is a high-severity cross-site scripting vulnerability in appium-mcp, published on 13 Jul 2026. An attacker can exploit it over the internet without logging in, and only if a user opens a file or follows a link.
Official description
MCP Appium is an MCP server that provides AI assistants with tools to automate mobile app testing on Android and iOS. In versions prior to 1.85.10, the 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. This issue has been fixed in version 1.85.10.
Weakness: CWE-79
Which versions are affected by CVE-2026-58500?
2 open source packages ship an affected version, including appium-mcp. It affects 1 product.
| Package | Affected | Fixed in |
|---|---|---|
appium-mcp npm | All versions | 1.85.10 |
appium-mcp npm | All versions | 1.85.10 |
Products include Appium Appium-Mcp.
How do I fix CVE-2026-58500?
Upgrade appium-mcp to 1.85.10 or later.
Escape output for the context it lands in and set a strict Content Security Policy. Upgrading the affected component is the real fix. More about Cross-site scripting.
Is CVE-2026-58500 being exploited?
It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-58500 exists.
Sources
Also known as GHSA-x975-rgx4-5fh4.