The security initiated its protocols and terminated any chances of the money being stolen in 30 seconds making the hackers lose 5 ETH.
Bridges like this one are meant for external chan transactions from one network to another by locking in tokens on the protocol. Rainbow operates on ETH, NEAR, and AURORA and has over $2.3 bln in circulation according to the data.
The hacker was probably trying to trigger the system to unlock the tokens without initially puttin in any funds. This method is nothing new and has been used numerous times to go around other blockchain security systems helping steal money, in some cases up to $200 million in case of the infamous Nomad exploit.
Thankfully Rainbows automatic validators have immediately noticed the fraud and captured the falls block keeping it from further processing and secured the deposited 5 ETH put in by the hacker.
RBE - Red BIOS Editor Download
Version: 1.0.6
License: free
OS: Windows