Mage talent · row 4 of Frost, from level 25 (20 with Talented 5/5) · Physical

Shatter

Increases the critical strike chance of all your spells against Frozen targets by 17/33/50%.

Game files · build 1.60.1.70291Read from the WoW Forever beta client, build 1.60.1.70291.

Compared with Classic

Classic tooltip

Increases the critical strike chance of all your spells against frozen targets by 10%.

Data	Classic	Forever
effect 1 aura	aura (112)	dummy (server script) (4)

What Blizzard said about Shatter, each line checked against the files.

Matches the files
Shatter: No longer has Improved Frost Nova as a pre-requisite.
The files Shatter (11170) has no prerequisite in 70291; Classic required Improved Frost Nova. It is 3 ranks at 17/33/50% (Classic 5 ranks up to 50%).
Shatter Improved Frost Nova Class deep dives: Mage and Shaman

69876 Sep 16First beta build we archived. No changes in the client files since.