Instead of extracting, right-click the file in 7-Zip and select "Open Archive" . This lets you see the file names inside without potentially triggering a malicious script.
Knowing if it was on a USB drive , a server , or inside a specific software folder will help me give you a much more accurate assessment. old.7z
If you find a file named "old.7z" that you did not create—especially if your other files have disappeared—it may be an encrypted container created by malware. Instead of extracting, right-click the file in 7-Zip
If you didn't create it, be cautious. Compressed archives can store malware. 2. 💻 Software Repositories (e.g., GitHub) Instead of extracting
Use an updated antivirus or VirusTotal to check the archive.