Report it privately through GitHub's vulnerability reporting, not in a public issue. Say what you found, how to reproduce it and which version you ran (ymcp version). You get an answer within a few days; the fix ships in the next release, and the advisory is published with it.

Only the latest release gets fixes. ymcp update, or your package manager, moves you to it.

ymcp holds YouTrack passwords and tokens, so these matter most:

• a password or token reaching a log, an error message, a tool result or anywhere outside the system keychain (or the config file where there is no keychain);
• the HTTP server answering without the token it was started with;
• a pipeline's loopback MCP server reachable by anything but its own agent;
• release archives, checksums or the Docker image that don't verify as described in the README.

A YouTrack account doing what its own permissions allow is not a vulnerability in ymcp.