The bug
A dispenser or dropper which is facing the world border or outside the world border can be activated. This means that it can for example spawn entities outside the world border or place blocks such as water, lava or powder snow.
Linked issues
Attachments
Comments
Can confirm in 21w03a.
Can confirm in 21w05b.
Can confirm in 21w06a.
Can confirm in 1.16.5 and 21w08b.
Can confirm in 21w17a.

Can confirm in 1.17 and 1.17.1 Release Candidate 1 (now dispensers can place powder snow outside of the world border).

Can confirm in 21w37a.

Can confirm in 21w38a.

Can confirm in 21w40a.

Can confirm in 21w41a.

Can confirm in 21w43a.

Can confirm in 1.18 Pre-release 1.

Can confirm in 23w03a
Can confirm in 20w51a.