Visual editor stripping IMG SRC arguments in Calypso and Gutenberg

[scherem]

When you make a mouseover link in the HTML editor and publish it works as expected. Soon as you switch to the visual editor, the code is stripped breaking the mouseover.

This does not happen in the WP-Admin editor.

Steps to reproduce

1. In HTML editor use the following code:

<a href="#"><img src="First Image Address" onmouseover=this.src="Second Image Address" onmouseout=this.src="First Image Address" /></a>

2. Switch to visual editor.
3. Switch back to HTML editor
4. Code is now displayed as:
   In Calypso:

<a href="#"><img src="First Image Address" /></a>

What I expected

I expect the HTML code not to change when you switch back to the visual editor or that the code is stripped out of the HTML version on save/preview.

What happened instead

The code is stripped as shown above.

Browser / OS version

Chrome

Screenshot / Video

WP-Admin

Gutenberg:

Context / Source

We'd also love to know how you found the bug: #manual-testing, #user-report
User brought the issue into chat (6568843-hc). After testing, a ticket was made to examine further 1428593-zen.

Upon further testing, discovered that code behaves as expected in WP-Admin.

[scherem]

Tested the issue in Gutenberg and found it existed too (but behave differently). Updated above to reflect this.

[stale]

This issue has been marked as stale and will be closed in seven days. This happened because:

• It has been inactive in the past 9 months.
• It isn't a project or a milestone, and hasn’t been labeled `[Pri] Blocker`, `[Pri] High`, `[Status] Keep Open`, or `OSS Citizen`.

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