If you fear a browser extension-based vulnerability (like an XSS vulnerability that allows an attacker to send all of a visitor's passwords to their server), use a native application like KeePass. You lose some convenience, but it's just a few extra steps when logging in and registering.
It's certainly not impossible that some major flaw will eventually be found in KeePass, but it's stood the test of time so far, and it's hard to imagine how it could be mass exploited considering it basically just reads and writes a local AES-encrypted file. Even if someone finds something that lets you completely bypass the encryption (which is very unlikely), they'd still need to gain access to your hard drive (or wherever you're storing the file).
But I'd also say the net security benefit of a lot more people using something like LastPass or 1Password would still outweigh the damage of a future vulnerability.
Either way, there is really no excuse for password reuse in 2018, especially when your password for managing your super popular software package running on an enormous amount of devices is the same as the password to your Harry Potter fanfic forum account or whatever.
It's certainly not impossible that some major flaw will eventually be found in KeePass, but it's stood the test of time so far, and it's hard to imagine how it could be mass exploited considering it basically just reads and writes a local AES-encrypted file. Even if someone finds something that lets you completely bypass the encryption (which is very unlikely), they'd still need to gain access to your hard drive (or wherever you're storing the file).
But I'd also say the net security benefit of a lot more people using something like LastPass or 1Password would still outweigh the damage of a future vulnerability.
Either way, there is really no excuse for password reuse in 2018, especially when your password for managing your super popular software package running on an enormous amount of devices is the same as the password to your Harry Potter fanfic forum account or whatever.