To show an impression of the route we show a static google maps image with waypoints and a polyline. Like this:
The polyline is calculated everytime the user saves the route and stored in the database.
We noticed at one point that static images were not displayed in Firefox and after hours of research we found out that Firefox automatically escapes backticks in URL’s while Google Chrome and Internet Explorer do not. We do not URL encode the polyline (as this is already encoded) so the backticks were echo’d out to the URL of the image. However because the URL was signed server side, changing it afterwards generates an invalid signature and makes the request fail.
So to solve the problem: Escape backticks (and a few other characters) before signing the URL resulting in the same behaviour across all browsers.
Borderline of this short post: There is a difference across browsers where Firefox force URL encodes backticks while Chrome and IE don’t.