Added a comment

UIKit+AFNetworking/AFImageDownloader.m

@@ -110,6 +110,13 @@
 @implementation AFImageDownloader
 
 + (NSURLCache *)defaultURLCache {
+    // It's been discovered that a crash will occur on certain versions
+    // of iOS if you customize the cache.
+    //
+    // More info can be found here: https://devforums.apple.com/message/1102182#1102182
+    //
+    // When iOS 7 support is dropped, this should be modified to use
+    // NSProcessInfo methods instead.
     if ([[[UIDevice currentDevice] systemVersion] compare:@"8.2" options:NSNumericSearch] == NSOrderedAscending) {
         return [NSURLCache sharedURLCache];
     }