[Plugin: Add Meta Tags] HTML breaks if tags include quotes

If I tag a post as ‘”test tag”‘ (i.e. including the double quotes), this plugin (v1.8) fails to escape or strip the quote marks, and the the HTML produced:

<meta name=”keywords” content=”foo, “test tag”, bar” />

is thus invalid.

While tagging with quotes is not sensible, it may happen, and should be catered for, per Postel’s Law.

(It may be better if WordPress simply stripped quotes from tags)
is thus invalid.

The same problem occurs with the ‘Dublin Core for WP’ plugin, as reported at ‘plugin-dublin-core-for-wp-html-breaks-if-tags-incude-quotes‘.