ACUX scales the CAPTCHA images horizontally and vertically. The original images are not a consistent size, so sometimes the scaling is minor.
Other times, it's quite significant. https://en.wikipedia.org/w/index.php?title=Special:Captcha/image&wpCaptchaId=703624476 is 224x66.
It's scaled to 270x60 regardless.
Version: master
Severity: major