When there's base64 encoded stuff in it, it's usually like that to hide a backdoor. Most PHP backdoors have scripts to execute system commands on the server.

Its a late reply, but since I have been using IBPro Arcade for almost 4 years wanted to give my feedback.

We have been using IBProArcade for 3-4 years. And yes till this day today we are still using IBProArcade + 2.7.2. And since we started there has been more than 25 hacking attempts weekly on our forum for the past 3-4 years. But they never succeed.

Just because the files were discovered within its folder it doesnt mean IBProArcade was the cause of why the forum was hacked. Like Ozzy47 Replied. That doesnt prove it was the IBProArcade. I just want others to know that this is definitely not an IBProArcade issue.

Thanks for this final statement.

ibProArcade v2.7.3+ (10 years anniversary release) in on the track, but there were still no security-issues to be fixed, just internal improvements ect.