Corner variation which is not in Josekipedia
This question may look simple at first, but refuting the deviation is pretty difficult - there are no original sources on this to my knowledge.

Not answering the hane directly

$$Bcm1
$$ -------------------
$$ . . . . . . . . . |
$$ . . . . . . . . . |
$$ . . . . a 0 4 8 . |
$$ . . . . b 1 5 6 . |
$$ . . . . . . 9 7 . |
$$ . . . . . . 2 . . |
$$ . . . . . . . . . |
$$ . . . . . . 3 . . |
$$ . . . . . . . . . |


First off, let's try a different answer to white 6. Black could consider playing 7 at a or b, but I believe the result would be bad. It can be considered, though, if the board is right.

Hane at a could lead to a complicated fight, probably involving an exchange, but I could not tell if it is better for either player.

$$Bcm1
$$ -------------------
$$ . . . . . . . . . |
$$ . . . . . . . . . |
$$ . . . . 3 O O . . |
$$ . . . . 1 X X O . |
$$ . . . . . . 2 . . |
$$ . . . . . . O . . |
$$ . . . . a . . . . |
$$ . . . . . . X . . |
$$ . . . . . . . . . |


The idea of b is to either magari-turn at 3 if white connect on the right, switching to the top instead of the right side all of sudden. This would be very unusual after blocking at 5 initially, and locally white gets a superior result. I presume that (apart from extending on the top) black would like to add a stone at a later to enclose white and get a reasonable outside shape. Either way black is not thick.

$$Bcm1
$$ -------------------
$$ . . . . . . . . . |
$$ . . . . . . . . . |
$$ . . . a 2 O O . . |
$$ . . . . 1 X X O . |
$$ . . . . . . . 3 . |
$$ . . . . . . O . . |
$$ . . . . . . . . . |
$$ . . . . . . X . . |
$$ . . . . . . . . . |


If white instead opts to push from behind on the third line once more (at a) before returning to play 7, it is better than joseki for black. If white attempts to resist by jumping to a, black will not hane at 3 next, but push through at 2 and cut, involving a ladder.

In conclusion of this section, while an option to consider, I would not regard a different answer to the hane a refutation at all.

Reverting to joseki

$$Bcm1
$$ -------------------
$$ . . . . . . . . . |
$$ . . . . . . . . . |
$$ . . . 2 . O O O . |
$$ . . . . 1 X X O . |
$$ . . . . . . X X . |
$$ . . . . . . O . . |
$$ . . . . . . . . . |
$$ . . . . . . X . . |
$$ . . . . . . . . . |


After the deviation is played out, black could nobi at 1, with white jumping at 2. Seemingly, this is even because we returned to joseki.

$$Bcm1
$$ -------------------
$$ . . . . . . . . . |
$$ . . . . . . . . . |
$$ . . . . . O O 1 . |
$$ . . . . a X X . . |
$$ . . . . . . . . . |
$$ . . . . . . O . . |
$$ . . . . . . . . . |
$$ . . . . . . X . . |
$$ . . . . . . . . . |


However, instead of the usual move at a, black might consider playing at 1 instead. This leads to a different joseki, with emphasis on territory on the right edge. Losing this option is a loss for black. This in effect means that white's early hane is superior to joseki, which is impossible by definition. Accordingly, returning to joseki is not sufficient as a refutation of the deviation.

$$Wcm1
$$ -------------------
$$ . . . . . . . . . |
$$ . . . . . . . . . |
$$ . . . . . a O . . |
$$ . . . . . X X 1 . |
$$ . . . . . . . . . |
$$ . . . . . . O . . |
$$ . . . . . . . . . |
$$ . . . . . . X . . |
$$ . . . . . . . . . |


As a side note, the hane is sometimes played by white in a similar shape precisely when white is afraid of a black hane there instead of the usual nobi at a. This is an (uncommon) joseki.

So sum this up, we still have not found a viable refutation.

Hane

$$Bcm1
$$ -------------------
$$ . . . . . . . . . |
$$ . . . . . . . . . |
$$ . . . b 1 O O O . |
$$ . . . . a X X O . |
$$ . . . . . . X X . |
$$ . . . . . . O . . |
$$ . . . . . . . . . |
$$ . . . . . . X . . |
$$ . . . . . . . . . |


Another option is to hane at 1. In this shape, white has the options of cutting at a or clamp at b. Hane underneath is impossible since black would be most glad to just nobi-extend.

$$Wcm1
$$ -------------------
$$ . . . . . . . . . |
$$ . . . 4 2 . . . . |
$$ . . . 1 X O O O . |
$$ . . . . 3 X X O . |
$$ . . . . . . X X . |
$$ . . . . . . O a . |
$$ . . . . . . . . . |
$$ . . . . . . X . . |
$$ . . . . . . . . . |


After the clamp, descending at 2 is very dangerous. The sequence to 4 is the basic pattern likely to follow, but the fight is easier for white since black has no good response to a.

$$Wcm1
$$ -------------------
$$ . . . . . . . . . |
$$ . . . . . . . . . |
$$ . . . . X O O O . |
$$ . . . . 1 X X O . |
$$ . . . . . . X X . |
$$ . . . . . . O . . |
$$ . . . . . . . . . |
$$ . . . . . . X . . |
$$ . . . . . . . . . |


If white cuts, a fight involving a ladder will follow, possible leading to an exchange, as explained in a different answer. This can get pretty messy if both sides keep playing the strongest moves.

Leaping ahead

$$Bcm1
$$ -------------------
$$ . . . . . . . . . |
$$ . . a 2 . . . . . |
$$ . . c 1 b O O O . |
$$ . . . . . X X O . |
$$ . . . . . . X X . |
$$ . . . . . . O . . |
$$ . . . . . . . . . |
$$ . . . . . . X . . |
$$ . . . . . . . . . |


Black is not forced to hane, he can consider a keima, too. Usually, white would attach at 2, leaving black with the options of a, b, c or tenuki. Since white was lowered to the second line, I consider this a superior for black.

$$Bcm1
$$ -------------------
$$ . . . . . . . . . |
$$ . . . c . . . . . |
$$ . . . 1 2 O O O . |
$$ . . . b a X X O . |
$$ . . . . . . X X . |
$$ . . . . . . O . . |
$$ . . . . . . . . . |
$$ . . . . . . X . . |
$$ . . . . . . . . . |


In case white plays 2 instead, bumping against the black single stone, black should consider either covering at a or the strong nobi at b.

$$Bcm1
$$ -------------------
$$ . . . . . . . . . |
$$ . . . b . . . . . |
$$ . . a X O O O O . |
$$ . . . c 1 X X O . |
$$ . . . . . . X X . |
$$ . . . . . . O . . |
$$ . . . . . . . . . |
$$ . . . . . . X . . |
$$ . . . . . . . . . |


In case black covers at 1, it is difficult to clamp at a, because white lacks an as effective attack on the 5 (instead of 4) black stones.

Crawling on the second line at b once or maybe twice is an option, in both cases probably leading to white gaining sente. Locally, the result is very bad compared to joseki, but white finished in sente twice, which is very valuable, too.

There is also the option to cut at c. This fight should be acceptable for both.

$$Bcm1
$$ -------------------
$$ . . . . 4 . . . . |
$$ . . 3 2 . . . . . |
$$ . 5 . X O O O O . |
$$ . . . 1 6 X X O . |
$$ . . . 8 7 . X X . |
$$ . . . . . . O . . |
$$ . . . . . . . . . |
$$ . . . . . . X . . |
$$ . . . . . . . . . |


In case black plays strongly, white will aim to exploit the increased cut aji, likely starting with the hane at 2. This way, white gets life while getting enclosed by a thin black group.

However, black can consider different moves (e.g. 5 at 6, or even 3 at 6).

$$Wcm1
$$ -------------------
$$ . . . . . . . . . |
$$ . . . . . . . . . |
$$ . . . X a O O O . |
$$ . . . . 1 X X O . |
$$ . . . . . . X X . |
$$ . . . . . . O . . |
$$ . . . . . . . . . |
$$ . . . . . . X . . |
$$ . . . . . . . . . |


As per the comments, there is a very strong variation with white cutting immediately. If black cuts at a, it will return to the situation that requires a black ladder.

$$Wcm1
$$ -------------------
$$ . . . . . . . . . |
$$ . . . . . . . . . |
$$ . . . X 3 O O O . |
$$ . . . 4 1 X X O . |
$$ . . . 5 2 . X X . |
$$ . . . . . . O . . |
$$ . . . . . . . . . |
$$ . . . . . . X . . |
$$ . . . . . . . . . |


Without said ladder, black will have to hane from the outside at 2. The sequence to 5 will follow, leading to a fight. Black's shape seems relatively poor so this should be carefully examined before playing the keima.

Conclusion

If black specifically wants to avoid a fight, he can always chose to play the simple nobi (6 in the previous diagram) to revert to the usual joseki.

On the other hand, despite the vast number of possibilities that arise from the keima, I believe this to be the best option in case black wants to resist and does not mind a fight.

So we could say that black has gained far more options than he lost by white's deviation, thus refuting white's move.

However, likely the early hane is a only tiny mistake.