Web font has changed
After the software was updated, the font of the webpage was changed
Hi , you can allow websites to choose the own fonts in options this is turned in by default. if it is turned off you can turn it on by opening menu -> Options -> type 'font' in search bar -> under font & colors select Advanced -> Allow pages to choose their own fonts, instead of your selections check the box restart Firefox and reload the website.
Looks you changed from a sans serif font to a serif font. Maybe check the default font settings in "Options/Preferences -> General".
You can also check for font issues in Font Book.
You can right-click and select "Inspect Element" to open the builtin Inspector with this element selected.
You can check in the Rules tab in the right panel in the Inspector what font-family is used for selected text. You can check in the Font tab in the right panel in the Inspector what font is actually used because Firefox might be using a different font than specified by the website.