I don't think this has anything to do with Plogger. It looks like an issue with Geeklog's Media Gallery Module prior to 1.4.8b (see here). Did you used to use Media Gallery? If so, there may be a cached search somewhere that scammers have found and are trying to exploit the vulnerability for the previous install of Media Gallery on your server. However, they are now trying to scam a URL that is now using Plogger (which does not have the same vulnerability) and it's throwing a warning.
You really should not have any issues with this attack while using Plogger.