Could you please compare 1Password and 1PasswordX from the security point ?
I can use both of them and want to choose one of them from the security point of view.
Both extensions are secure because they are based on the same security design the whole 1Password system is based on. Because of these general security guidelines that they share, it would be difficult to "compare" the two extensions, and it might not even make a lot of sense to do so.
However, in addition to the basic security principles (such as end-to-end encryption), the main difference is that 1Password X runs entirely in your browser, and therefore has some specific security measures built-in because it runs in the browser rather than in a traditional OS. You can see the list of these measures (including a description for each of them) here.
Ultimately, it is up to you to choose which extension you prefer, but when it comes to the security aspect, there isn't really a clear winner as both of them are based on 1Password's core security and privacy principles.
Thank you for answer.
It works in entirely in the browser and it can be a new vector of attacks. I don't know how the browser works and this is the reason of my question. For example, there is a vulnerability in the browser and one malicious extension can get data of another extension...
Or 1PasswordX excludes such ability ?
1Password X runs inside a sandboxed environment to prevent malicious scripts interfering with it, but malicious extensions always pose a risk. The only way to remove this risk is to avoid installing questionable extensions altogether. At the very least, you should confine them to a separate browser profile if you really need them despite this.
If you create a separate browser profile just for your browsing and 1Password X, 1Password will be isolated from other malicious extensions installed on your system.