The question is in title.
My wife notice that my avatar changed from the last time she saw it. Being blind, I did not pay attention to this.
Now, it is very pale yellow. Is there a way to restore it as it was before ?
Thanks in advance
For those of you wondering "why?", the best I can understand the various conversations on StackExchange Meta is:
Previously generated icons used some of users' personally identifying information as part of the random number fed into the avatar generating algorithm.
This is now seen as a security problem, i.e. someone could take your avatar image and recover data about you they are not supposed to have. (I don't know if some hashing algorithm has recently been inverted, or they are thinking more seriously about security now, or what else has changed to make this a problem they are addressing.)
Regardless, they are currently recreating avatars that had previously been generated. I believe if you uploaded your avatar explicitly nothing will change, but, if you, like me, have just always kept the avatar they gave you at sign-up, you can expect it to change soon.
This was linked in the comments, but I feel it should be preserved in a more permanent form: Profile image changes (Gravatar images won’t be recoverable after email change) . The relevant quote is
Why is this change even affecting Gravatar?
Stack Overflow uses a hashed version of your email address to access your Gravatar image. If your email address changes, we simply can no longer access that Gravatar URL. This wasn't a problem when your Per-Site Email was frozen in time. Now that your main email will actually affect that URL, your Gravatar profile image might be lost. We will keep displaying the image as long as you’re using it, but it will disappear from the image selector if you change your email.
We've recently discovered a vulnerability in our identicon generation process. To remedy it, we have changed how we approach generating them and regenerated all identicons. We do not have any indication that any personally identifiable information (PII) was leaked as part of this vulnerability.
Since 2013, we've been salting all identicon hashes, but still using email and IP addresses to generate them. Because of the sensitive nature of this type of data, we're moving entirely away from this method and instead will use an implementation going forward that does not involve any user-related information. Out of an abundance of caution, we're also forcibly changing all identicons across the Stack Exchange network, and chose to wait to communicate the change to you until the process was further along.
This is a result of the way in which SE handles email. There are two major concerns here:
Gravatars were generated using a hashed version of a user's email address. Because of this, there are concerns that Gravatars might leak private information. There is no evidence that this actually has happened, but better safe than sorry.
Because Gravatars are generated from an email address, if a user changes their email, their Gravatar will change. Historically, this hasn't been a problem, as SE has used one's original email address for all time. However, SE has recently moved away from this, and has made it easier for users to change their email address in the SE system. The problem is that changing one's email address could now lead to their Gravatar also changing. This, again, leaks private information (i.e. that the email address of a user has changed.