Steps to replicate the issue (include links if applicable):

open hewiki (version upgrades a day before most other wiki), on article פולינום (polynomial). same in cawiki.

all formulas are turned to ugly red error messages with huge text. the crux of the error looks like so:
("Math extension cannot connect to Restbase.") מהשרת "http://localhost:6011/he.wikipedia.org/v1/v1/":)

clearly, "localhost" there is out of place - readers do not run local server listening on port 6011 on their own machines.

this is a serious breakage, afflicting any article using the <math> tag or any template using it, and is going to hit all the major wikis in less than a day. ( hewiki and cawiki get the new version a day earlier than most other wikipedias )
can't assign priorities myself, but i would call this "critical".

peace.

What should have happened instead?:
math formulas should be displayed as math formulas instead of the error message

Software version (skip for WMF-hosted wikis like Wikipedia):
1.41.0-wmf.12 (e54da81)

Other information (browser name/version, screenshots, etc.):

unfortunately, screenshot in hebrew... :)