[Please HELP] Serious problem with my WP sites

Hi guys, something's very weird happening with my WP sites.. Both of them are on the same hosting, but different domains. Different themes, different plug-ins. Well, the only thing in common is the same hosting between them, nothing more.

Here's the problem: today suddenly my sites stopped loading. I can log-in to admin panel, but the site homepage and none of the posts aren't showing. I checked my files and noticed that index.php file is blank (!) on both sites. I mean, WTF, how could they get blank? I did not edit them or something. Okay, so re-edited them and the sites started loading, BUT just about after few seconds my sites redirect to some CPA/PPI offers randomly. And the index.php files get blank again. After I re-edit the index.php sites, sites load, but again - redirect to some shitty offer and the file gets blank again..

I am thinking that my sites could have been hacked and someone is redirecting visitors of my sites to their offers.. But why in the hell the index.php files get blank by themselves? Anybody might have an idea what's happening and how could I resolve this issue?

looks like they may have been hacked, ask you host to check. Did you have easy admin or password and any security plugins in place?
Do you have a backup copy of your site saved?

The hosting or your sites are compromised. I suggest to switch your hosting and check for any backdoors or shells in your files. Also try to disable any recent plugins your have installed and check the htaccess file if there are any redirects from there also.
Hope this helps. Cheers

Your site have been hacked. Delete the htcaccess files and change your permalink.. That should solve the problem... for now.

Just checked the htaccess files and they are empty lol. Nothing is written inside them. I did contact support of my host, they said they'll run a clamscan. If they won't be able to help, will try switching hosting, but if I copy my files, any infected files will be copied too... So probably will have to install a fresh wordpress and copy the whole site content by hand. That's a lot of work so hope can resolve this without such hassle

UPDATE: Okay, everything seems to be fine now. I deleted some plugins, my hosting company ran a calmscan, updated the cores of wordpress for both sites. Don't know, which of these actions helped, but everything seems to be back to normal now. Thanks guys for your help too!

now what you should do is download and install the duplicator plugin and make a copy of your whole site and all the settings and save it somewhere safe. Then if it happens again you have your complete site ready to install. Just uninstall wordpress then re install using your saved file - easy and can only take a few minutes to be back up again. Duplicator plugin is free from wordpress.org, i use it on all my sites so i know it works

Scan your website with free online scanner "sucuri" and see what's the result you get.

Try using some nulled theme/plugins, that might help again to show those offers, jk