“Fraud and deceit abound in these days more than in former times.”

‘Unreasonable Claims in Social Affections and Relations’, Chapter IX.
Friends in Council (First Series), (1847),

Book 2, Ch. 13
Discourses on Livy (1517)

The Tragedy of Irene (1749), Act III, Sc. 2
Context: To-morrow's action! Can that hoary wisdom,
Borne down with years, still doat upon tomorrow!
That fatal mistress of the young, the lazy,
The coward, and the fool, condemn'd to lose
A useless life in waiting for to-morrow,
To gaze with longing eyes upon to-morrow,
Till interposing death destroys the prospect
Strange! that this general fraud from day to day
Should fill the world with wretches undetected.
The soldier, labouring through a winter's march,
Still sees to-morrow drest in robes of triumph;
Still to the lover's long-expecting arms
To-morrow brings the visionary bride.
But thou, too old to hear another cheat,
Learn, that the present hour alone is man's.

Columbus (1844)

Psychic Scams Steal Millions From Unwitting Victims https://web.archive.org/web/20180126040018/http://www.miaminewtimes.com/news/bob-nygaard-helps-psychic-scam-victims-9397958, Miami New Times (6 June 2017)

Diary (23 July 1851)
Diary and Letters of Rutherford Birchard Hayes (1922 - 1926)
Context: Is there anything in which the people of this age and country differ more from those of other lands and former times than in this — their ability to preserve order and protect rights without the aid of government? … We are realizing the paradox, “that country is governed best which is governed least.” I no longer fear lynch law. Let the people be intelligent and good, and I am not sure but their impulsive, instinctive verdicts and sentences and executions, unchecked by the rules and technicalities of law, are more likely to be according to substantial justice than the decisions of courts and juries.

Il est plus facile d'être amant que mari, par la raison qu'il est plus difficile d'avoir de l'esprit tous les jours que de dire de jolies choses de temps en temps.
Part I, Meditation V: Of the Predestined, aphorism LXIX.
Physiology of Marriage (1829)

No source for this quote among Orwell's writings has yet been located, and the earliest published source of this phrase found on Google Books is this snippet https://books.google.com.mx/books?id=kWD0AAAAMAAJ&q=%22truth+is+a+revolutionary+act%22&dq=%22truth+is+a+revolutionary+act%22&hl=en&sa=X&ved=0ahUKEwjs0MKSqpbKAhWH0iYKHXj6ABUQ6AEIJjAD from p. 5 of Science Dimension, Volumes 14–18 (1982) published by the National Research Council Canada. Quote Investigator has an article "In a Time of Universal Deceit – Telling the Truth Is a Revolutionary Act" http://quoteinvestigator.com/2013/02/24/truth-revolutionary/ indicating their attempts to trace the quote. The earliest similar remarks they had found were in a 1982 book titled “Partners in Ecocide: Australia’s Complicity in the Uranium Cartel” by Venturino Giorgio Venturini, where the word “universal” was omitted, and a specific originating text was not identified: "In a time of deceit, telling the truth is a revolutionary act."
Variants:
During times of universal deceit, telling the truth becomes a revolutionary act.
In an age of universal deceit, telling the truth is a revolutionary act.
In a time of universal deceit, telling the truth is a revolutionary act.
Speaking the Truth in times of universal deceit is a revolutionary act.
Truth is treason in an empire of lies. (Often attributed by Ron Paul to Orwell but never sourced.)
In the mid-19th century Karl Georg von Raumer made a remark, which has a similar meaning. In Geschichte der Pedagogic (1855), he states: 'Jede keimende Wahrheit ist revolutionär gegen den entgegenstehenden herrschenden Irrthum, jede keimende Tugend revolutionär gegen das im Schwange gehende, ihr widersprechende Laster' which translates as: "Every germinating truth is revolutionary against the opposing ruling error, every germinating virtue is revolutionary against popular contradictory lies."
In 1898 French socialist Jean Jaurès said, "When a society, when an institution, lives only by lies, truth is revolutionary." He was speaking with reference to the ongoing Dreyfus Affair. The statement is quoted in Ruth Harris, The Man on Devil's Island: Alfred Dreyfus and the Affair that Divided France (2010), p. 262. (She cites Le petit Meridional, 3 July 1898, as the original source.) This seems very close in spirit and in phrasing to the pseudo-Orwell quotation. (The cumulative index to the many volumes of Orwell's writing compiled and edited by Peter Davison does not reveal any direct references to Jaurès or the Dreyfus Affair.)
Disputed
Variant: In a time of universal deceit, telling the truth is a revolutionary act.

Source: 2000s, The Age of Turbulence (2008), Chapter Nineteen, "Globalization and Regulation", p. 375.