Spam post showing in my wp site

I’m using wordfence free version. Recently I noticed an unwanted post(ad) appearing in my blog posts. But this post does not belong to my website. I can’t see this post when I’m in wp-admin mode. Only visitors can see this unwanted post. There is no sign of this post in my wp-admin mode. Affected page screenshot:
– https://drive.google.com/file/d/1HI_H2SubISKfFqIWoYTcBdd3fSJ7FVcA/view?usp=drivesdk
– https://drive.google.com/file/d/1HKw62Fo0N9RsUFvoQv5h43IZbh_HUWh0/view?usp=drivesdk
Steps I have taken below mentioned.
– Deactivated all plugins
– Installed wordpress default theme
Still unwanted post appearing in my blog. Please help me. What should I do now?

The page I need help with: [log in to see the link]