sooperset/mcp-atlassian < 0.22.0 lacks path validation in confluence_upload_attachment, passing client file_path to open(file_path,"rb") in src/mcp_atlassian/confluence/attachments.py via _upload_attachment_direct(). An authenticated MCP client can read any server-accessible file and upload it to Confluence as an attachment, exposing env vars (e.g., CONFLUENCE_API_TOKEN). Upgrade to 0.22.0.