Hydrogen peroxide can act both as an oxidising as well as reducing agent. Expalin.

Explanation

The change in oxidation number accompanyin the decomposition of `H_(2)O_(2)` is as follows:

Since oxygen atom in `H_(2)O_(2)` can undergo an increase as well as decrease in oxidation number therefore, it can act both as reducing as well as oxidising agent. This is supported by the following reactions.
As reducing agent:
`" " overset(+1)(AgO)+underset("Reducing agent")(H_(2)overset(-1)(O_(2))) to 2overset(0)(Ag)+H_(2)O+overset(0)O_(2)`
In this reaction, `H_(2)O_(2)` acts as reducing agent and has reduced `Ag_(2)O` to metallic Ag.
As oxidising agent:
`" " Pboverset(+2)S+underset("Oxidising agent")(4H_(2)overset(-1)(O_(2))) to Pboverset(+6)(SO_(4))+4H_(2)O^(-2)`