Adblock Plus was reported not that long ago for some sort of security flaw, can't remember what it was. If you use either Firefox or Chrome, uBlock Origin is better than Adblock Plus as it's less resource-intensive and is reported to be safer.
Also, anyone who uses Windows needs to upgrade to 10 and should also install Spybot Search & Destroy to activate its Immunization feature (which locks out a huge number of known malware hosts). Anyone who's not using Windows is reasonably safe from most malware.
And anyone who uses Firefox in particular may want to consider installing NoScript, which can whitelist (or blacklist) JavaScript on a per-site basis.