electerm: Path traversal in FTP/SFTP recursive folder download via unsanitized server filename

electerm is an open-sourced terminal/ssh/sftp/telnet/serialport/RDP/VNC/Spice/ftp client. Prior to 3.15.120, electerm allows a malicious FTP or SFTP server to write attacker-controlled content outside the selected download directory because recursive transfers in src/client/components/file-transfer/transfer.jsx pass server-supplied file.name and folder.name values to resolve without sanitization. This issue is fixed in version 3.15.120.