Erm... I'm rather new here, and very confused. Can someone explain to me what a "UA dump" is, why it's an exploit, what it has to do with griefing, what it was threatening and how, and how commanders flocking to Colonia is fixing it?
A "UA dump" is selling thargoid items (originally called "Unknown Artifacts" - UAs - so the name has stuck even though it's no longer accurate) to a station's black market. Selling a few here and there is basically harmless, but selling them in large bulk will shut down almost all station services.
You get a week's warning on Galnet when the shutdown threshold is reached, and if corrective action is not taken the station shuts down.
Corrective action consists of delivering a large quantity of Meta-Alloys to the affected station. This can take place proactively to prevent the shutdown or reactively to repair a station which has been shut down. Delivery of Meta-Alloys can also be used as preventative action to increase the number of UAs needed to damage a station in the first place.
So, the commanders currently flying out to Colonia with holds full of Meta-Alloys will sell them at the station (before Tuesday 6th), with sufficient volume to cancel out the UA sales ... and probably then a few tens of thousands more ... and prevent the shutdown.
UA dumping is not itself an exploit, but there have been suggestions made that some sort of exploit may have been used to either collect or transfer the UAs (which can only be found relatively close to the Pleiades) all the way to Colonia. Only Frontier will know for sure whether that's true or not - it's certainly *possible* to do this without an exploit, and people have done so over similar distances in the past.
As it shuts down most station services - basically everything except a very limited commodity market to sell the meta-alloys to - it can be used to inconvenience other players, and therefore some people consider it griefing (either in all cases, or just in some specific cases). Regardless of whether you want to apply that particular description, it is generally considered a hostile act against the station owner/supporters.