When administrators upload a new version of an extension to Plesk, the
possible conflicts between the existing and new files are resolved in
the following way:
- If a file already exists, it is overwritten.
- If a directory already exists, files inside it are overwritten.
- Files that were present in the previous version of an extension, but
are missing in the newer version, are removed.
If one of these conflict resolution rules is not satisfied (for example,
an existing file is blocked and cannot be overwritten), the upgrade
procedure fails.