CVE-2021-29488: Creation of files outside the Download Folder through malicious PAR2 files

SABnzbd is an open source binary newsreader. A vulnerability was discovered in SABnzbd that could trick the `filesystem.renamer()` function into writing downloaded files outside the configured Download Folder via malicious PAR2 files. A patch was released as part of SABnzbd 3.2.1RC1. As a workaround, limit downloads to NZBs without PAR2 files, deny write permissions to the SABnzbd process outside areas it must access to perform its job, or update to a fixed version.