Custom HTML is not stripped from post title

[eduardozulian]

It is possible to add custom HTML such as <em> or <i> to post and page titles and they will be rendered correctly when you visit the post.

Examples from WordPress.com:

• https://wordpress.com/forums/topic/italics-in-post-title/
• https://wordpress.com/forums/topic/how-do-i-italicize-in-the-title/

Expected behavior

To have HTML tags either:

• Transformed into the element. For example, <em>This is italic</em> shown as italic in the post list; or
• Stripped as we see in WordPress.com:

Actual behavior

We see the unstripped HTML tag in the posts list:

Steps to reproduce the behavior

1. Start a post
2. In its title, use some custom HTML like <em> or <i>
3. Save the post
4. Check the new post in the posts list

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Also reported for wordpress-mobile/WordPress-iOS#16999

[KirillPovarintsev]

Can I have it? I've got a fix (it should address the issue in multiple places across the app).