Can't find "virus" in Wordpress, what's the plan?

Question

Malware

Good afternoon!
There is a caching plugin. It creates a cached page, but pulls up a line with external links to it. There were 4 links in total. 2 of them I killed (were encoded in base64). There are 2 more left. I found in the database that they are formed by an SQL query:

Request

SELECT * FROM `information_schema`.`PROCESSLIST` WHERE (CONVERT(`ID` USING utf8) LIKE '%dlandroid24%' OR CONVERT(`USER` USING utf8) LIKE '%dlandroid24%' OR CONVERT(`HOST` USING utf8) LIKE '%dlandroid24%' OR CONVERT(`DB` USING utf8) LIKE '%dlandroid24%' OR CONVERT(`COMMAND` USING utf8) LIKE '%dlandroid24%' OR CONVERT(`TIME` USING utf8) LIKE '%dlandroid24%' OR CONVERT(`STATE` USING utf8) LIKE '%dlandroid24%' OR CONVERT(`INFO` USING utf8) LIKE '%dlandroid24%' OR CONVERT(`TIME_MS` USING utf8) LIKE '%dlandroid24%' OR CONVERT(`ROWS_SENT` USING utf8) LIKE '%dlandroid24%' OR CONVERT(`ROWS_EXAMINED` USING utf8) LIKE '%dlandroid24%' OR CONVERT(`TID` USING utf8) LIKE '%dlandroid24%')

Server: localhost » Database: information_schema » View: PROCESSLIST
Appears in the cached page.

<div style="display:none"><a href="http://dlwordpress.com/">Free WordPress Themes</a>, <a href="https://dlandroid24.com/">Free Android Games</a>

And there are 2 such lines, for 2 external links. I was prompted to find a file with permissions 777, but I xs how to look for it. I started learning php, mysql, etc., and I want to figure it out and fix it myself. But I can not.
Tell me where to dig? For example here:
http://5best.rf

Answer 1

Try to check with antivirus. For example AI-bolit

Answer 2

Let's just say that it's not even a virus, but a harmless insertion of your link from distributors of free templates (you know where free cheese happens). Antivirus may not even see this.
I would advise you to carefully study the theme files, especially footer.php
If it does not work out, then you need to carefully study everything. https://kwork.ru/configuration/8190/udalyu-levie-v... - you can use the services to remove such wickedness