Safety depends entirely on the source. In general, .7z files are safe containers, but they can be used to hide malicious software if downloaded from untrusted sites.
Never open an archive from an unknown sender or a suspicious website. Use a reputable antivirus tool to scan the file before extraction. How to Open the File KPP0333a.7z
Some "fake" 7-Zip websites have been known to distribute malware alongside the tool. Safety depends entirely on the source