Malicious Code detected

Scanned my Site with Quttera Web Malware Scanner two malicious Scans are detected:

1)
Severity: enMaliciousThreatType
File: /wp-content/plugins/wp-slimstat/admin/config/maintenance.php
File signature: 5888209ebdd7df9ac51dc7a11f6db1da
Threat signature: 9d6f6dec2d8a024f50ba7a47201c0c29
Threat: $_REQUEST[‘f’]…
Details: Detected malicious PHP REQUEST

2)
Severity: enMaliciousThreatType
File: /wp-content/plugins/wp-slimstat/…/wp-slimstat-reports.php
File signature: 2e28fbaf20c9304d11e56ac6664e53ae
Threat signature: f968ed48652d44e54b59fd61be8aa2a5
Threat: <?php class wp_s
Details: Potentially Malicious obfuscated PHP threat

Is it malicious code indeed or harmless code by slimstat?
If malicious what´s to do?

Thanks for reply.
Conrad