Lektor before 3.3.11 does not sanitize DB path traversal. Thus, shell commands might be executed via a file that is added to the templates directory, if the victim's web browser accesses an untrusted website that uses JavaScript to send requests to localhost port 5000, and the web browser is running on the same machine as the "lektor server" command.
The product uses external input to construct a pathname that is intended to identify a file or directory that is located underneath a restricted parent directory, but the product does not properly neutralize special elements within the pathname that can cause the pathname to resolve to a location that is outside of the restricted directory.