General updates -Addressed issues to further ensure an enjoyable gaming experience.
So what "issues" have been addressed, exactly? As suspected, the recently discovered duplication glitches have been patched out. This includes both the table and mailbox glitches, and a number of YouTubers have now uploaded videos demonstrating how these glitches no longer work.
The Nintendo-focused YouTube channel Blaines provided a summary:
Exploits without hacks...have actually been patched. That includes the mailbox exploit...the table exploit...and anything else...I think no clipping out of bounds as well - all this stuff is patched, so the economy - at least for honest playing people - is back to normal.
If you don't want your experience to be impacted by these changes, it's as simple as not performing the most recent update. The downside is you'll no longer be able to play locally or online with others.