Updated on Oct. 21 at 2:16 p.m. ET — As of around 2 p.m. ET on Wednesday, both the Internet Archive and Wikipedia appear to be back online. Wikipedia's status page is still showing the issue as unresolved, but Down Detector reports for both sites are at near-zero at the time of publication.

Updated on Oct. 21 at 12:03 p.m. ET — A spokesperson for the Wikimedia Foundation, which runs Wikipedia , told Mashable that the outage was related to newly discovered security vulnerabilities in PHP , which is what Wikipedia is built on.

“The Wikimedia Foundation is currently in the process of addressing security vulnerabilities in PHP , the programming language that underpins most wikis, including the Wikimedia projects. This issue affects all known versions of PHP, and is not specific to the Wikimedia Foundation," the spokesperson said. "All Foundation-supported systems and volunteer-run systems that use PHP are affected.…