Saracens wing Chris Ashton has been cited for allegedly making contact with the "eye(s) and/or eye area" of Ulster centre Luke Marshall.
Ashton, who was recalled into the England squad by new head coach Eddie Jones last week, appeared to wrap both arms around Marshall's head during Saturday's European Champions Cup Pool 1 match.
A disciplinary hearing will now take place on Jan. 20 and if a sanction is imposed it could possibly delay Ashton's return to the international stage after being on the fringes for the last two years.
"EPCR has received a citing complaint against the Saracens wing, Chris Ashton [No.14], following the European Rugby Champions Cup Round 5 match against Ulster Rugby on Saturday, 16 January 2016," a European Professional Club Rugby statement read.
"Ashton is alleged to have made contact with the eye(s) and/or eye area of the Ulster centre, Luke Marshall [No.13], in the 16th minute of the match in contravention of Law 10.4 (m)."
Marshall was one of two Ulster tacklers tying up Saracens full-back Ben Ransom early on in Saracens' 33-17 triumph, with the incident coming as Ashton tried to keep the ball alive for his side.
It was spotted by the citing commissioner and the 28-year-old will now wait to see if his chances of playing for England for the first time since June 2014 have been dealt a blow.
Clermont's Viktor Kolelishvili also faces a potentially anxious wait after a bizarre incident in which he pushed referee Wayne Barnes during his side's 21-13 defeat at Ospreys.
The Georgia flanker was lined up in defence around the fringes of a ruck when he shoved the English referee, who was stood in front of him keeping an eye on the breakdown.
At the time the 26-year-old escaped with just a telling-off, but his case will now be reviewed at a hearing on Jan. 19.
Glasgow's Ryan Wilson has also been cited after being "alleged to have grabbed the testicles" of Northampton scrum-half Lee Dickson.
Under World Rugby's laws, which cover "testicle grabbing or twisting or squeezing", Wilson could also face a potentially lengthy ban at a hearing on Jan. 20.
Wilson's Glasgow team-mate Tim Swinson will have a hearing on the same day after he allegedly punched Northampton hooker Mikey Haywood in the 74th minute of their 19-15 defeat at Franklin's Gardens.
Newport replacement hooker Rhys Thomas has also been cited after he was alleged to have bitten Castres back row Thomas Caballero in their European Challenge Cup clash.
The 33-year-old allegedly bit Caballero in the 67th minute of Newport's 31-18 win over the Top 14 side.