The 2nd editions of Seaside and Prosperity have brought rewordings for some types of effects. Those types of effects also exist on cards in other expansions, so it makes sense to change those cards as well.
A bunch of cards get wording and functional changes in Dominion Online. Those cards are expected to be printed with those wordings once their expansions get their next print run.
There are some more cards that get a wording update without a functional change. Again, those cards are expected to be printed with those wordings some time in the future.
The 3 Hinterland cards with errata can be found at the end of the list (they were originally excluded to prevent spoilers)."On-buy" triggers
Effects triggering on or otherwise being dependent on buying a card are removed and generally replaced with one of two options: Either triggering simply on gaining, or triggering on gaining a card you bought.
Note that Hermit now exchanges itself for a Madman, so does not deplete its own pile in the process.Overpay
Technically also belonging to the above category, the 4 overpay cards from Guilds get errata using the "Overpay" keyword. You overpay now simultaneously with paying for the card when you buy it (in the online game, you are asked immediately afterwards). The overpay effect is now timed as a "when gain" trigger, so happens after the overpay card was gained. This has consequences, for example Herald can now topdeck itself! While in play
Card effects under a dividing line that worked "while in play" now have that effect as part of the normal on-play effect of the card, limited to the turn it was played. That means that effect is successfully Throneable, but also that it is no longer active when the card is played using a Way or under effects like that of Enchantress.Keeping Durations "alive"
When a card is removed from play due to an external effect, keeping track of effects or gained resources may become hard. If it happens for a Duration card, the next turn effect has to be remembered for a potentially long time. The following errata prevents cards from doing their "destructive" effects to Duration cards.
Bonfire got a much simpler wording, it can only trash Coppers now.More Command
Cards get the Command type usually because they play a card in a special place, leaving it there, and often they are prevented from playing Command cards. This is to make sure that there is no loop of cards, playing each other in turn, without using up a resouce (as the card played itself is not "used up" and in play as usual). Recent errata and playtesting revealed that some more cards need to get/give this type to prevent potential loops.
Prince is now a Command card and can no longer set aside Command cards. Inheritance turns Estates into Command cards (in addition to Action).Miscellaneous
A few cards were given errata that doesn't really fit the above categories, usually to make their text simpler and/or easier to understand.
Storyteller gives you +1 Card directly now, without the detour over +$1. Herbalist uses a wording similar to Scheme to get its effect done (which is now also Thronable). Alchemist, with its dependence on a Potion in play for the topdecking effect, now works earlier, before you may have "accidentally" topdecked that Potion with Herbalist.
Donate does its effect now just before you draw your hand for the next turn, no longer "overriding" Outpost's reduced hand size.
Mountain Pass happens now directly after the Province gain. That means if you plan to do multiple buys, save the Province for last (previously, the debt would only occur at end of turn). Similarly, gaining that Province in your Action phase will seriously hamper you buy potential this turn already.
Innovation just got more flexible, you can now play any gained Action, it doesn't have to be the first gained, but are still limited to do that once per turn.Hinterland cards
Of the 3 cards, only Farmland has gotten a "non-standard" errata. Gaining another Farmland would allow you to instantly pile them if you gain one and have a Fortress in hand (which you can trash again and again to gain all the Farmlands that are still in the Supply).Non-functional changes
The following cards are getting non-functional changes:
Alchemy: Philosopher's Stone
Cornucopia: Young Witch, Horn of Plenty, Diadem
Adventures: Caravan Guard, Hireling, Mission, Champion
Empires: Encampment, Settlers, Bustling Village, Farmers' Market, Temple, Wild Hunt, Haunted Castle
Renaissance: ExperimentAdditional changes implemented
The relatively recent rule clarification that returning to your Action phase from your buy phase (via gaining Villa or Cavalry) triggers "end of buy phase" effects (Wine Merchant, new Merchant Guild) will also be implemented.