Bit tricky to reproduce as caching comes in to play, but here's how I replicated it:

1. Insert Code Macro into page.
2. In the macro title, enter '获取当前工作目录'.
3. Save the page.

Replication method 1:

1. Flush Confluence cache.
2. Flush browser cache.
3. Edit page again, characters in title will show up as empty boxes.

Replication method 2:

1. Access your server from another computer, using a LAN or VPN connection.
2. Edit page again, characters in title will show up as empty boxes.