The Rune Scribe prestige class (from Unearthed Arcana: Prestige Classes and Rune Magic) has the 4th level Living Rune feature:
At the end of a long rest, you can choose to increase one ability score of your choice by 2 or increase two ability scores of your choice by 1. At the end of each subsequent long rest, you can alter this choice, reducing the scores you previously increased and improving different scores. (If you chose to increase two abilities, you can opt to alter only one of those choices.)
This feature is meant to be similar to the Ability Score Improvement feature that other regular classes have, but those features also specifically say:
As normal, you can't increase an ability score above 20 using this feature.
However, this ability from the Rune Scribe doesn't specifically say that you can't break the ability score limit of 20 - and I don't know how the prestige classes of previous editions behaved, hence my reason for the question.
Can the Living Rune feature increase your ability scores over 20?