Is there a malicious code inside my wordpress site?
Probably.
Carefully follow FAQ – My Site Was Hacked – WordPress Codex.
Then take a look at the recommended security measures in Hardening WordPress – WordPress Codex and Brute Force Attacks – WordPress Codex
Change all passwords. Scan your own PC. Tell your web host you got hacked; and consider changing to a more secure host: Recommended WordPress Web Hosting – WordPress Codex