Rita Skeeter wrote in her Witch Weekly article (Goblet of Fire, Chapter 27):
Miss Granger, a plain but ambitious girl, seems to have a taste for famous wizards that Harry alone cannot satisfy. Since the arrival at Hogwarts of Viktor Krum, Bulgaria Seeker and hero of the last World Quidditch Cup, Miss Granger has been toying with both boys’ affections. Krum, who is openly smitten with the devious Miss Granger, has already invited her to visit him in Bulgaria over the summer holidays, and insists that he has ‘never felt this way about any other girl’.
However, it might not be Miss Granger’s doubtful natural charms which have captured these unfortunate boys’ interest.
‘She’s really ugly,’ says Pansy Parkinson, a pretty and vivacious fourth-year student, ‘but she’d be well up to making a Love Potion, she’s quite brainy. I think that’s how she’s doing it.’
Love Potions are of course banned at Hogwarts, and no doubt Albus Dumbledore will want to investigate these claims. In the meantime, Harry Potter’s well-wishers must hope that, next time, he bestows his heart upon a worthier candidate.
She is definitely trying to defame Hermione here, but she was a reputed journalist who always have some truth to say (her article on Dumbledore after his death was a masterpiece). Even in this case, she correctly gave secret information about she dating Viktor Krum and he inviting her to Bulgaria. About Love Potion, she even quotes Pansy Parkinson.
Other than that, Viktor Krum was a celebrity-class person who should easily have access to hot girls. He getting attracted to a nerdy girl who is also claimed by Pansy Parkinson to be ugly doesn't make sense. He also insisted that he "never felt this way about any other girl" (Emphasis is Rita Skeeter's, not mine). Apparently, he seemed to have love feelings for Hermione, but he didn't pursue her after he left Hogwarts (possibly because Hermione couldn't feed him more Love Potion to keep the love alive). So, this thing requires real investigation.
As to how Hermione procured the Love Potion, we know for sure that Hogwarts girls used to smuggle Love Potion from Weasley Twins' shop, but the shop didn't exist during Goblet of Fire. I don't know about any other shop (in Hogsmeade or Diagon Alley) selling Love Potion which brings us possibility of she stealing it from Sluhorn's cabinet. Given, the only vial was stolen by Romilda Vane, the another possibility is she brewing it herself by stealing the ingredients from Sluhorn's cabinet. Exactly the Pansy Parkinson's claim which is what makes it so realistic (you know high school girls have too many ears all over the school).
If you look at the video in which Slughorn introduced Love Potion to the class, Hermione could identify it by smell (I know she was into books, but could books provide smell?).
What is most interesting in this is that all girls except Hermione got attracted to the potion. Except Hermione. Yes. This is exact criminal attitude. She either already had her hands on Love Potion or she didn't want to look suspicious on future stealings.
Did Hermione use Love Potion on Viktor Krum? Any words from Rowling or a solid logical interference from other excerpts? Only canonical answer please.