If you do find a "working" code that is stolen or generated via exploits, Rockstar will eventually detect it. Their ban policy for fraudulent licenses is permanent—not just for GTA 5, but for your entire Rockstar Social Club account. You lose access to any legitimately purchased Rockstar games (Red Dead Redemption 2, Max Payne 3, etc.) tied to that account.

Instead of chasing fake activation codes, consider these legitimate options:

Status: Not currently available, but worth knowing.

On May 14, 2020, Epic Games Store gave away GTA 5 for free—permanently. Over 15 million people claimed it. If you missed that window, you cannot go back. However, Epic repeats massive giveaways annually. Sign up for their newsletter. If they ever re-offer GTA 5 (or a similar premium title), you claim it once, and a Rockstar Activation Code is automatically linked to your Epic account.