Zimbra's sudo configuration permits the zimbra user to execute the zmslapd binary as root with arbitrary parameters. As part of its intended functionality, zmslapd can load a user-defined configuration file, which includes plugins in the form of .so files, which also execute as root.
Screen 5.0.0 when it runs with setuid-root privileges does not drop privileges while operating on a user supplied path. This allows unprivileged users to create files in arbitrary locations with `root` ownership, the invoking user's (real) group ownership and file mode 0644. All data written to the Screen PTY will be logged into this file, allowing to escalate to root privileges