An issue was discovered on Xiaomi Mi WiFi R3G devices before 2.28.23-stable. The backup file is in tar.gz format. After uploading, the application uses the tar zxf command to decompress, so one can control the contents of the files in the decompressed directory. In addition, the application's sh script for testing upload and download speeds reads a URL list from /tmp/speedtest_urls.xml, and there is a command injection vulnerability, as demonstrated by api/xqnetdetect/netspeed.