I use Illustrator files as source documents for complex system maps that we export to SVGs for applications. With the most recent updates, the exports have significantly changed the output code for the SVG which is impacting the javascript interactions with those svgs. The first and most substantial issue is that in calculating the viewbox attribute parameters, Illustrator is NOW including hidden layers where it once ignored them. I use a background layer which mimics our system's background colors to more closely reflect the contrasts needed and hide that for export. But where once the svg tag exported as
<svg xmlns="http://www.w3.org/2000/svg" viewBox="0 0 1317.04 755">
it now exports as
<svg xmlns="http://www.w3.org/2000/svg" viewBox="0 0 1407 791">
which shifts all the other object coordinates within the svg, unless I actively delete that layer from the illustrator file.

Keep in mind that for the above example, nothing in the Illustrator file was altered between the two exports other than the Illustrator update.

I've also noticed that bold text once carried a font weight and now omits that.