1862517 - Sanitize breaking CSS when replying to messages

Status: RESOLVED DUPLICATE of bug 1731198

(Thunderbird :: Message Compose Window, enhancement)

Description

[Martin]

Steps to reproduce:

Reply to an email (using the HTML composer) that contains some CSS that significantly changes how the text that I am composing is rendered. Specifically, some Microsoft products seem to include the following CSS in all messages:

<style type="text/css" style="display:none;"> P {margin-top:0;margin-bottom:0;} </style>

Actual results:

It seems like the "paragraph" style is broken. There is no spacing between paragraphs, so they behave just like "body text". Choosing "remove all direct formatting" has no effect.

Expected results:

The paragraph style should work normally, regardless of what may be contained in a quoted email, contained in the reply that I am composing.

One possible solution would be to strip CSS that will give the appearance of breaking the composer from quoted replies, and instead insert the formatting directly into the HTML elements of the quoted message. Another to just offer to delete the CSS without attempting to fix up the quoted message. And a third might be to add a class to the affected elements in the quoted message and move the styling to refer to that class.