Hi I'm wondering if there is a word for this: An advertisement sticker for a legitimate product or service is placed without permission on conspicuous property (e.g. often on public traffic signage, or a curbside box where newspapers are sold or distributed) in order to promote that product or service. Calling the sticker 'an advertisement' seems inadequate because the advertisement occupies the same space as graffiti, 'tagging', or other vandalism. I don't know of a word for this form of advertisement. Lacking one I created the neologism 'vandaltisement'. Better ideas/suggestions for other words are welcome.

Note that I'm talking about an advertisement for a legitimate product or service, not about an advertisement for an event, such as a flyer promoting a one-time event or concert, posted in a conspicuous place without permission, although this type of advertisement maybe related.