We opined it may be vulnerable (4,4)
I believe the answer is:
wide open
'vulnerable' is the definition.
(I've seen this before)
'we opined it may be' is the wordplay.
'we' becomes 'w' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'it' becomes 'e' ('e' can mean 'electronic' which is similar to 'IT').
'may be' indicates an anagram.
'opined'+'e'='opinede'
'opinede' anagrammed gives 'ideopen'.
'w'+'ideopen'='WIDE-OPEN'
Can you help me to learn more?
(Other definitions for wide open that I've seen before include "Gaping" , "Vulnerable to attack" , "with unpredictable outcome" .)