PsiTransfer is an open source, self-hosted file sharing solution. Prior to version 2.4.3, the upload PATCH flow under "/files/:uploadId" validates the mounted request path using the still-encoded "req.path", but the downstream tus handler later writes using the decoded "req.params.uploadId". In deployments that use a supported custom "PSITRANSFER_UPLOAD_DIR" whose basename prefixes a startup-loaded JavaScript path, such as "conf", an unauthenticated attacker can create "config.<NODE_ENV>.js" in the application root. The attacker-controlled file is then executed on the next process restart. Version 2.4.3 contains a patch.