Wikipedia clearly is among the most innocuous websites and one can not imagine it being blocked by a child pornography filtering mechanism. However, the improbable has just occurred in the UK. The whole problem began when an image of a Scorpions album prompted Internet Watch Foundation’s Cleanfeed child pornography filtering system - used by many of the leading UK ISPs - to block the particular page.
Consequently, all traffic to Wikipedia from ISPs that deploy Cleanfeed beagn to be routed through transparent proxies – one proxy per ISP. Even if a single user is barred from editing by Wikipedia’s anti-vandalism system, all other users using the same proxy suffer exactly in the same fashion as most UK-based Wikipedia users are sharing a handful of IP addresses.
You can track the problem as it unfolds on this Wikipedia page dedicated to it. The IWF has stated on its website that the particular page was reported through its online reporting mechanism. After it was found unsuitable for minors, the page was “added to the list provided to ISPs and other companies in the online sector to protect their customers from inadvertent exposure to a potentially illegal indecent image of a child.”