Short answer

Exchanges (PDF) mandate brokers to display a notification mentioning all the surveillance measures on the instrument when the client tries to place an order.

This nudge is displayed when either the promoter’s pledged holdings exceed 50% or when 20% of total outstanding shares, including both promoter and non-promoter holdings, are pledged (PDF).

After clicking on Buy for such stocks, another nudge will appear. Click on Proceed to purchase the stock. This requirement aims to ensure that investors make informed decisions before buying a specific stock.