I'm a little bit paranoid to login to my GOG account from my browser, instead of the launcher, but I have to if I want to vote on the Dreamlist.

I've been logging in via browser for ages and never had a problem.

*blink* Why would it be unsafe? And didn't you do so in order to post here? Do you not log on anywhere else from browsers? E-mail, social networks, stores...?
(Of course, I would never touch Galaxy or clients in general and their very existence on a system looks potentially unsafe to me.)

Are you paranoid for a specific reason, or, is there a general fear that the browser (or, the GOG web site itself) is somehow tainted?

For (nearly) 13 years, I have been logging into GOG via various internet browsers (and had only briefly tried the GOG Galaxy client in 2015), with no issues whatsoever.

I'm here from the launcher. I go to a game from the store, click on the forum of the game, and than go to the community from there. Over a decade ago I watched a YouTube video where a guy was talking about Steam, and he said that it's safer to login from the launcher just in case. Since than it just become natural to me to always login from launchers when it comes to video games. I just think that it's easier to hack an account if you login from the launcher. I might be completely wrong but it's like an OCD I guess.

Just in case of what? Do you happen to recall the reasons given for endorsing this practice?

If you account is hacked, either you gave your id to suspicious website or GOG server are hacked, and if the GOG server are hacked, even if you only use the app, your account will be hack too in the process so you are safe to use your browser to log in ONLY in the GOG website. It would be great if GOG could give us the option to use 2FA to protect more the account like all others stores but for now we only have e-mail 2FA.

Extreme Precautions:
Have an electronic mail address dedicated to your GOG account (which you would not divulge to anyone), with two-step login enabled. Both the mail and GOG account would have unique (and overly complex) passwords, not used prior with any other service.

Then, aside from people in your immediate [physical] vicinity, no one can commandeer your account unless GOG or your mail provider have been compromised in some manner. However, accounts are far more likely to be hijacked due to actions taken by the authorized user.

Edit: Corrected punctuation mistake.

Ah, OP's back with another fun topic to say that everybody should use gaming clients. This time illustrated by a "youtuber said".

Assuming your Web browser is Firefox, not some Google Chrome skin, it’s probably much safer to access your GOG account that way than going through GOG Galaxy.

I logged in, and voted on the Dreamlist. I also checked that my two step verification is enabled, which is something I could only see if I logged in the browser.
I use Google Chrome.
You can stop complaining now.

Personally I think its safer to use the browser instead of the app to browse. Imagine someone post something harmful (a link for exmaple) - a browser may attempt to block it especially if you have ublock origin. If you want buy - I would never use the app.

Then it’s too late, you can stop worrying about any kind of safety when browsing the Web.
(as far as I know, GOG Galaxy is based on Google Chrome too)

Well since no one had a reasonable response so far, I will chime in.

Browsers are more vulnerable. They provide a wider scope and vector for a bit of malware. A more probable accidental self inflicted harm, via a rogue website. Plus much more.

A client is specific to a vendor or brand. It is not as likely to get targeted by an attack, just because the specific nature an attack would require. As opposed to a password skim from a browser. Even using crap security in a client, the client is less probable to be harmed.

That being said, dont assume the client is better than offline installers. Get those and you are all set. As for logging into the site via the client. Im not your keeper. Make your own decisions, nobody here will care. Im just providing a perspective, regarding the query.