When adding > or < into an attribute value as follows:
<!-- wp:paragraph -->
<p><abbr title="1 > 2">False</abbr> and <abbr title="1 < 2">True</abbr></p>
<!-- /wp:paragraph -->
The serializer forces them to be > and < respectively.
<!-- wp:paragraph -->
<p><abbr title="1 > 2">False</abbr> and <abbr title="1 < 2">True</abbr></p>
<!-- /wp:paragraph -->
This gets rendered by WordPress as:
<p><abbr title="1 > 2″>False</abbr> and <abbr title="1 < 2">True</abbr></p>
The “False and” text is erroneously consumed be the attribute:

In this case, it seems to be a problem with wptexturize(), as it is converting the attribute closing " into ″.
But if the block serializer output > as > then this symptom could be avoided.
Possible regression after https://github.com/WordPress/gutenberg/pull/9963.
Relates to https://github.com/WordPress/gutenberg/issues/9915, https://github.com/WordPress/gutenberg/issues/8779, https://github.com/WordPress/gutenberg/issues/12683.
Tested in v5.7.0-rc.1.
Technically it would be a duplicate of #12683, though the earlier issue was intended to have been closed as a result of the merge of #9963.
I don't think it's entirely a regression of #9963, in that the element serializer itself is not the culprit, and it does still encode the characters.
I think the issue is a combination of RichText.Content effectively bypassing the serializer using RawHTML (source) and the behavior of the browser DOM in parsing a the paragraph contents as HTML, where > is normalized in this context to > (because, as noted in #9963, it is _not invalid_).
var d = document.createElement( 'div' );
d.innerHTML = '<p><abbr title="1 > 2">False</abbr> and <abbr title="1 < 2">True</abbr></p>';
console.log( d.innerHTML );
// "<p><abbr title="1 > 2">False</abbr> and <abbr title="1 < 2">True</abbr></p>"
So the blame lies entirely with wptexturize()?
So the blame lies entirely with
wptexturize()?
Technically it always has 😆 #9963 was always a bandaid workaround because nobody dared touch the texturize function.
Anything actionable? Is this still an issue?
@ellatrix This is still an issue as of v7.1.0-rc.1.
Most helpful comment
Technically it always has 😆 #9963 was always a bandaid workaround because nobody dared touch the texturize function.
https://core.trac.wordpress.org/ticket/45387