In IASKAppSettingsWebViewController.h, CFURLCreateStringByReplacingPercentEscapesUsingEncoding() is used, which is deprecated in iOS 9.0.
Xcode suggest to use CFURLCreateStringByReplacingPercentEscapes() "which always uses the recommended UTF-8 encoding."

The code will then be (last input argument 'kCFStringEncodingUTF8' is removed):

value =  CFBridgingRelease(CFURLCreateStringByReplacingPercentEscapes(kCFAllocatorDefault,
                                                                                      (CFStringRef)value,
                                                                                      CFSTR("")));

CFURLCreateStringByReplacingPercentEscapes() is supported since iOS 2.0, so it can be used safely.