This is the second theft from Balancer in a month, after it warned of a critical vulnerability on August 22, and that vulnerability was exploited for around $2 million several days later.
Balancer frontend compromised
Balancer issued an urgent warning to stop using its web interface, as it was evidently compromised by malicious actors who redirected the funds to themselves. Within 30 minutes of the tweeted warning, $240,000 had already been stolen.