I do not have access to real-time data or specific changes in Facebook's platform. However, I can provide some general information on how Facebook Stories work and possible reasons for the "other" viewer you're seeing.
Facebook Stories are short-lived posts that are visible to your selected audience for 24 hours. When you set your story to "Friends only," it should only be visible to your approved friends on Facebook. However, there could be a few reasons why you see an "other" viewer:
App Glitch or Bug: Sometimes, social media platforms can have glitches or bugs that cause unexpected behavior. The "other" viewer might be a result of such a technical issue, and it may not necessarily mean someone unauthorized is viewing your story.
Misinterpretation of Privacy Settings: Double-check your privacy settings to ensure your story is indeed set to "Friends only." Sometimes users may accidentally change settings or post stories publicly without realizing it.
Friend Requests and Pending Friendships: It's possible that someone has sent you a friend request, and while the request is pending, they may still be able to view your story. However, this depends on Facebook's specific privacy policies and settings at the time.
Friend's Privacy Settings: Even if your story is set to "Friends only," if one of your friends has their account set to public, someone who is not your friend could view your story through their account.
It's important to remember that social media platforms can change their privacy settings and features over time. If you are concerned about privacy, it's best to review your settings regularly and be cautious about the content you share.
Regarding knowing who the "other" viewer is, Facebook generally provides limited information about who views your stories to protect user privacy. They may only show the list of people who have seen your story if they are your confirmed friends, and in some cases, the list may not be exhaustive.
As this information might be outdated by the time you read it, I recommend checking Facebook's official help center or community forums for the latest information on privacy settings and story views.