According to Odaily Planet Daily, regarding the technical details of the Balancer theft, kebabsec auditor and Citrea developer @okkothejawa posted on the X platform, stating, "(The check error mentioned by @moo9000) may not be the root cause, because in all 'manageUserBalance' calls, ops.sender == msg.sender. The security vulnerability may have occurred in a transaction before the creation of the contract for withdrawing assets, as it caused some state changes in the Balancer vault."