What the vulnerability does
01Description
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.
