frontend.php triggering Wordfence

Hi Team,

Wordfence found the following new issues on “#####”.

Alert generated at Sunday 3rd of May 2020 at 05:22:56 AM

See the details of these scan results on your site at: https://#######.com/wp-admin/admin.php?page=WordfenceScan

Medium Severity Problems:

* Modified plugin file: wp-content/plugins/squirrly-seo/models/Frontend.php

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Why would this file be changed ? Is this the sign of being hacked ?

PS : I did not upgrade this plugin . its already latest version . This alert just popped up today .