SiYuan vulnerable to RCE via zip slip and Command Injection via PandocBin

Summary

### Summary Siyuan is vulnerable to RCE. The issue stems from a "Zip Slip" vulnerability during zip file extraction, combined with the ability to overwrite system executables and subsequently trigger their execution. ### Steps to reproduce 1. Authenticate 2. Create zip slip payload with path traversal entry `../../../../opt/siyuan/startup.sh`. startup.sh contains malicious code like: ```bash #!/bin/sh echo 'you have been pwned' > /siyuan/workspace/data/pwned.txt echo "pandoc 3.1.0" ``` 3. Upload zip to workspace via `/api/file/putFile` 4. Extract zip via `/api/archive/unzip`, overwrites the existing executable `startup.sh` while maintaining the +x permission 5. Trigger execution by calling `/api/setting/setExport` with `pandocBin=/opt/siyuan/startup.sh`. This calls `IsValidPandocBin()` which executes `startup.sh --version` that outputs "pandoc 3.1.0" and executes any arbitrary malicious code