Tumblr, the short-form blogging and reblogging service, was serving child pornography that had slipped through standard filters. This explains why the app was abruptly pulled from the iOS App Store on Friday, with little explanation from Apple or Tumblr. Apple previously removed Telegram for similar reasons.

In a statement, Tumblr explained that it works closely with partners such asely with our industry peers and partners like the National Center for Missing and Exploited Children (NCMEC) to actively monitor content uploaded to the platform. Every image uploaded to Tumblr is scanned against an industry database of known child sexual abuse material, and images that are detected never reach the platform.

A routine audit discovered content on our platform that had not yet been included in the industry database. We immediately removed this content. Content safeguards are a challenging aspect of operating scaled platforms. We’re continuously assessing further steps we can take to improve and there is no higher priority for our team.”

There still aren’t any details on when the Tumblr app might return to the App Store, but the social network says the offending content was removed and that it is working with Apple to make the app available. Throughout this situation, Tumblr has remained available via the Play Store for Android users despite the brief availability of child pornography.