kmessinger on "editing source code HTML of a wordpress page or post"

One way is to use a plugin like https://wordpress.org/plugins/better-search-replace/

Another is to sign into your hosted account and use phpMyAdmin which should be provided by your host.

Whichever or whatever, make sure you have a backup of the database.

I am no sure how you got rid of the malware but they usually leave a backdoor. You need to start working your way through these resources:

• https://codex.wordpress.org/FAQ_My_site_was_hacked
• https://wordpress.org/support/topic/268083#post-1065779
• http://smackdown.blogsblogsblogs.com/2008/06/24/how-to-completely-clean-your-hacked-wordpress-installation/
• http://ottopress.com/2009/hacked-wordpress-backdoors/

Additional Resources:

• http://sitecheck.sucuri.net/scanner/
• http://www.unmaskparasites.com/
• https://blog.sucuri.net/2012/03/wordpress-understanding-its-true-vulnerability.html