Online advertisements for some of Singapore's biggest brands have popped up unwittingly on incendiary websites, such as those that promote hate speech.
Such incidents are shining a spotlight on programmatic advertising - the use of algorithmic tools that automate the placement of advertisements online.
A video ad by the National Environment Agency (NEA) appeared on a website that has articles supporting the Islamic State in Iraq and Syria.
Ads for local retailer chains, banks, airlines and telcos were also found on other controversial websites, including one that has content from preachers linked to terrorism.
When contacted, most of the brands and the NEA said they were not aware that their ads had shown up on these sites, and voiced concern that their brands might be wrongly associated with the dubious content.
All of their ads have since been removed. Spokesmen for the brands said they regularly update their exclusion list with new sites, keywords and categories. They added that they would look into the matter and take it up with their advertising agencies.
An NEA spokesman said its ad was part of a broader online media campaign.
He added: "(We) will continue to monitor our outreach efforts, to ensure that future advertisements do not appear on unsuitable websites."
A Ministry of Communications and Information spokesman said: "Public sector agencies must avoid inappropriate associations that may create negative perceptions or undermine the public sector's messages."
Mr Bryan Tan, president of the Internet Society (Singapore), a non-profit organisation, said: "The danger of being caught up in a controversy is higher in the online world due to the use of programmatic advertising."
Dr Adrian Yeow, senior lecturer at SIM University's School of Business, said the unintended consequences include a public relations nightmare as the advertisers could be seen to be supporting a wrong cause, and the inadvertent funding of extremist content.
Programmatic advertising relies on computer programs to automatically serve advertisements onto multiple websites instantly.
The biggest provider in this space is Google via its AdWords advertisement booking and management system. Media agencies also buy from Google on behalf of advertisers.
Google's AdWords system allows advertisers to take their campaigns off undesirable websites by their specific addresses, but this process tends to be tedious.
Another option is to filter by categories such as "sexually suggestive", "profanity and rough language" and "death and tragedy".
Google said it has "a zero-tolerance policy" for content that incites violence or hatred, noting that the websites in question do not violate its policies. It added that it will continue to work with the industry to help it make informed choices.
The industry association, Interactive Advertising Bureau Singapore, said brand safety is a key concern for the industry, and it is an issue on which it is working closely with all stakeholders. Its spokesman said: "The organisation is committed to its mission of education and awareness, to shift advertiser considerations in digital beyond click-based metrics and one that emphasises context, quality of audience and compelling creative."
