This has proven itself, most recently as password manager leader LastPass admitted that they were not only hacked, but their source code was stolen.
“We have determined that an unauthorized party gained access to portions of the LastPass development environment through a single compromised developer account and took portions of source code and some proprietary LastPass technical information," LastPass said in a statement.
Fortunately, the company has told its customers that their personal and confidential information was not breached, and that they did not need to take any steps such as changing their passwords.
However, this does not change the fact that a password manager can be a single point of failure that could affect your personal dealings and those of your company. We stress, and will continue to stress, that password managers are objects of desire for hackers. Thus, they will always be under attack. Don't use them.