The explanation is 2,000 words long. It does not make a huge amount of sense, but apparently blames the pornographic images on an experiment Webb was performing to see whether or not someone was using malware embedded on porn sites to infect electoral candidates with malware that would prevent them from filing their candidacy before the deadline.
https://www.techdirt.com/articles/20160516/15010634454/dear-politicians-least-close-those-porn-tabs-before-sending-out-your-campaign-screenshots.shtml
