Impact label assignment

1) https://bugs.chromium.org/p/chromium/issues/detail?id=1139963#c9 the `Security_Impact-Stable ` label was manually assigned.
2) https://bugs.chromium.org/p/chromium/issues/detail?id=1139963#c40 ClusterFuzz assigned `Security_Impact-Beta` and removed `Security_Impact-Stable`, although the regression range was pointing far into the past
3) https://bugs.chromium.org/p/chromium/issues/detail?id=1139963#c45 the `Security_Impact-Beta` label was manually replaces with `Security_Impact-Stable` again

Now ClusterFuzz shows that the crash impacts Stable too. Did ClusterFuzz learn it from the bug tracker, or did it succeed reproducing the issue on stable?

If the latter, why did ClusterFuzz put the Beta label in the first place?