Is it safe to set permissions of a subfolder of a web server to 777? [duplicate]

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• Is it safe to CHMOD directories 777 on a VPS? 1 answer

I have a web application which works as a front end to experiments running on a computational server. The computational server writes files directly to a subfolder in /var/www/html of a LAMP server. The computational server uses a key to login to the web server and copy the files into that subfolder.

Now, security wise, is this safe. I mean, can anybody who doesn't have the password or key to that webserver somehow hack that subfolder. If someone can infact crack this, what alternate mechanism I can use to copy data from the computational server to the web server?

P.S I am the sole user of that webserver. I am just concerned about attacks from outside.