appium-mcp-server through 0.1.61 fails to validate or normalize file paths in the write_file and write_files_batch tools, allowing attackers to write files outside the intended PROJECT_ROOT directory. Attackers can supply absolute paths or relative paths with parent directory segments to overwrite arbitrary files with the server user's privileges, including shell profiles and configuration files in the home directory.

appium-mcp-server versions through 0.1.61 contain a path traversal vulnerability in the write_file and write_files_batch tools. The server fails to validate or normalize file paths, allowing attackers to write files outside the intended PROJECT_ROOT directory. Attackers can exploit this by supplying absolute paths or relative paths containing parent directory segments (e.g., ../). This enables overwriting of arbitrary files with the privileges of the server user. Sensitive targets include shell profiles and configuration files located in the home directory. The vulnerability poses a significant risk as it can lead to privilege escalation or persistent backdoor installation. No authentication bypass is required beyond access to the MCP server tools.