Solana announced that an attack affected more than 7700 wallets. The exploit affected several wallets, including Slope and Phantom.

Experts recommend that affected wallets should be transferred to cold wallets, and for those who do not have cold wallet, transferring all fund to a centralized exchange will be a good option.
Analysts says that technique of the attack is still unknown and a bug may cause this instead of Solana blockchain itself. A 0-day vulnerability seems more possible to gain access to such a large number of private keys.
According to Elliptic, blockchain analyzer, $5.8 Million crypto asset stolen just in August, including SOL, USD and NFT.