Anyone could go on internet archives website and either bribe or threaten someone to make changes.
And how is that different to any other form of evidence?
Eye witnesses can be tampered with.
Expert witnesses can be tampered with.
SOCO's can be interfered with to add/delete/substitute crime-scene evidence.
Evidence in storage can be tampered with.
Judges can be tampered with.
Jurors can be tampered with.
That's why, generally speaking, a suite of evidence is needed (although there might be a single piece that is more persuasive than any others) to convict someone.
This and that and that and that and that all point to me having eaten the cake.