All objects "bleed" white onto the sky or background colour in a reflection probe. Emissive objects bleed is much stronger. Invisible on white/black background colour.

Repro Steps:

1) Open attached project and scene "Test"
2) Observe reflection in sphere (from probe)

NOTE: Left red cube (emissive), right red cube and blue plane bleed onto background colour. None bleed onto other objects.
Changing background colour in probe to white/black hides issue (mid-tones and sky all reproduce)
Bleed gets wider/narrower when ref probe resolution is lower/higher respectively