Ivan Sproule snatched the winning goal for Linfield against Glentoran but was sent-off for taking his shirt off while celebrating the 82nd-minute strike.
The former Northern Ireland winger had been booked earlier in the game and got a second yellow for removing his shirt.
The Glens, fifth in the table, struck first when Steven Gordon swept the ball in at the far post on 26 minutes after David Scullion's cross from the left.
Linfield equalised just before half-time through Sammy Morrow.
The Blues are four points ahead of Crusaders who moved into second-place by beating Cliftonville in the north Belfast derby at Solitude.
It sets up an intriguing clash for New Year's Day when the Crues host Warren Feeney's league leaders at Seaview.
In Thursday's clash at Windsor Park, Linfield had the first big chance when Morrow shot wide from a good position in the box.
At the other end keeper Ross Glendinning pulled off a fine save to keep out a close-range Gordon header.
However, midfielder Gordon was not to be denied when Scullion's delivery from the left somehow eluded everyone at the near post.
Gordon forced it in and the Glens were scenting a first Boxing Day win at Windsor.
Linfield levelled when Stephen Lowry found Morrow who spun to beat his marker and shoot low underneath keeper Elliott Morris.
That is how it stayed until Andrew Waterworth played the ball through for Sproule to score the winner.
Sproule then ran to place his shirt on a corner flag which he lifted and waved in celebration.
That earned him a red card from referee Andrew Davey, but the Blues saw the game out with 10 men.
Linfield skipper Jamie Mulgrew: "It was the biggest crowd we have had in a long time, and the most important thing to the fans is the result.
"They are going home with the bragging rights and that means we have done our job.
"We have moved to the top of the table and the results have given us more belief.
"We have a togetherness and fighting spirit, and are looking like a team which is hard to beat."