For those interested in the specific risks of various L2s as they stand, L2Beat has the best overview: https://l2beat.com/?view=risk
While the various L2s are all pretty bleeding edge, the current state/alternative [1] is that a majority of the TVL is being bridged to alternate L1s, where the bridges are also extreme weaknesses [2]. There was the recent $320M Wormhole hack [3], the last record white-hat payout ($2M bounty on $850M at risk with the Polygon Bridge) [4][5], and $2.2B sits on Avalanche's Bridge [6] which is an EOA that is secured by literally 4 SGX machines. [7]