[halis]

I would do my best to fix it in the time allotted, but in the end, if it isn't fixed, it's going to take more time.

They could fire you or your whole team and that won't fix the bug either, in fact, that will make it take much longer as they'd have to hire replacements that won't be up to speed.

I would work hard to solve the issue, keep my mouth shut and if it wasn't finished by the next day and someone asked me about it I would tell them about my progress but that I needed more time.